Clinton has already inspired more fictional impersonations than any sitting president. Michael Douglas in The American President played Clinton as the White House seducer he might legitimately have been if Hillary had conveniently died young. Gene Hackman in Clint Eastwood's Absolute Power dramatised the long-rumoured Clinton dark side - Arkansas gossip about rape, murder and drug running - which moved from innuendo to constitutional crisis during the Lewinsky affair.

In The West Wing, Martin Sheen as President Bartlett is visually a post-Clinton dreamed-up leader (grey-haired, red-faced, sexually energetic), with useful hints of a past commander-in-chief. Sheen played JFK in the mini-series Kennedy and seems to use some of those famous Bostonian inflections here.

Writer Aaron Sorkin also seems to have drawn on those two stories. Bartlett is distanced from recent presidential history by having a loving, apparently faithful relationship with his wife, although she maintains a separate career as a doctor - a fantasy about the tolerance of the American electorate which would probably irritate Hillary Clinton more than anything else in this drama.

But Bartlett does possess a politically lethal secret. He ran for election while hiding a diagnosis of multiple sclerosis. This works as a metaphor for Clinton's duplicity - avoiding the viewer asking "which one is Monica?" - yet also draws on the way Jack Kennedy hid a degenerative kidney condition which might in time have done the work of Oswald's bullet.

If identification is one problem in political fiction, the other is ideology. The reason that audiences are much higher for dramas than for news shows is that the majority of the population is bored by the theories and techniques of politics, though occasionally turned on by its personalities.

The West Wing addresses this focus-group resistance by placing in the foreground the urgent and gossipy surface of politics. The President collapses with a fever (a hint of his hidden medical condition) on the eve of the State Of The Union address, while a Washington website has just reported that the White House chief of staff is a recovering alcoholic and drug-abuser. These crises are interspersed with comedy from the Rosencrantzes and Guildensterns of the administration - bitchy and ambitious aides who aspire to running the country but can't organise their own love lives.

If it merely consisted of these scenes, The West Wing would still be re-elected unopposed most Monday nights by those with Sky. It would, though, be Reaganite drama: all jokes and smiles and no hard choices. What's so impressive about The West Wing is that it's genuinely informative about politics - although a few of its policies prevent it from being entirely a dream ticket. Even Sheen can't manage to save the obligatory scene in which he quotes from the Constitution with soaring strings behind.

It would be good one day to have a Clinton-Lewinsky Behind Closed Doors, but, until then, The West Wing is smart, tough stuff. With the exception of the 1970s Trevor Griffiths series Bill Brand, about a Labour MP, British TV drama has usually treated politics as comedy (Yes, Minister, House Of Cards) or fantasy (A Very British Coup.) Americans are more solemn about politics, but The West Wing achieves the difficult feat of dramatising the nuts and bolts of office while also showing you the screws.

Just as a doctor I know once admitted that she had occasionally picked things up from ER which could be of use in treating a nasty head trauma, so The West Wing gives a weekly crash course in the US political system.

Like ER, TWW relies on a script so weightless in its brilliance, and characters etched with such finesse that you don't notice you've had the lecture until the credits roll.

Unlike ER, the corridors of power are static places full of chuntering about policy and committees, which makes TWW's achievement, or that of its creator, Aaron Sorkin, all the more remarkable.

Martin Sheen's president, Jed Bartlet, is a Kennedy without the womanising, a Clinton without the cigars or Whitewater. His team, from the irrepressible Sam Seaborn (Rob Lowe) to the brilliant but troubled Toby Zeigler (Richard Schiff), are all people we would dearly like to believe were really running the world.

It is hard to have favourites among the Bartlet ensemble, but CJ Cregg (Allison Janney), the harassed yet laconic press secretary is a fabulous invention.

But the real power of the series lies in its deep knowledge of the subject, which makes it almost uncomfortably prophetic.

An episode of TWW was pulled from E4, perhaps wrongly, on the evening of September 11. The plot revolved around a failed military sting in South America which resulted in the ambush and deaths of a US helicopter crew.

President Bartlet fumes: "Are you telling me our entire counter-intelligence service was fooled by a couple of guys with a ham radio and a shoulder-mounted rocket launcher?", only to muse later, "sometimes I wonder what the point of being a super power is any more".

Similarly, a couple of episodes later, a minor digression from the main plot brings the news that a known Islamist fanatic is thought to have slipped through the Canadian border.

"Should the FAA raise the level of security a notch?" asks the chief of staff. "What does that mean?", "It means people waiting an hour while their bags are scanned".

No security threshold was raised, little drama was caused. Powerful stuff.

We have romped through impeachment and polling, the cost of Aids drugs to the third world and funding the missile defence initiative. We know more about senators and subcommittees than a third-year American studies undergrad.

And throughout it has been a pleasure for those who like wit and style with their drama. In fact, the only thing wrong with TWW, is that it is just a television drama - however much we might wish otherwise.

The chief press officer, passing this titbit to an appreciative press conference, said, "By all means enjoy yourself." You can't fail to.

Yet does she get her name in the opening titles of The West Wing (Channel 4)? She certainly does not. It's tucked away, alongside Reporter #1, Economist #2 and Maid in the always-too-fast end credits of the US drama. For all its right-on, liberal, feelgood values, The West Wing could be a bit nicer to Mrs Landingham.

Too busy to bother with the feelings of a character actress in the late summer of her life, The West Wing is occupied with illustrating just what marvellous people liberals are. (We at The Guardian already know how smashing liberals are, but it's rather off-putting to see it on TV, especially as it's force-fed to the audience. With a straw. Up their nose.) While nasty folks on the religious right make veiled anti-Semitic remarks to Jewish members of the White House staff, President Josiah Bartlet (a hammy Martin Sheen) and friends demonstrate again and again that they're on the side of the angels. Making his grand entrance, he hobbles in quoting the Bible before telling the aforementioned religious types to "Get your fat asses out of my White House." Firm but fair.

And how fair the West Wing workers are. From the President down to assistants, everyone who works there is bubbling over with conviction, passion and human kindness. Rather than the cynical, selfish power-players who've been corrupted by the system, everyone on Potus's staff seems to have trained at the Maria Von Trapp Graduate School For Aspiring Political Types.

And they're so darned articulate - like Dawson (of Creek fame) and his friends all grown up. In Bartlet, America - or at least America's Democrats - has a President of whom it can be unashamedly, 100% proud. Full of homespun wisdom and mature world views, he's a moral leader, a loving husband, father and grandfather. Above all, he's A Good Man, the Potus with the mostest. Bartlet is not the kind of bloke to indulge in fellatio in the Oval Office. (Mrs Landingham would probably have a conniption fit at the mere mention of the word).

Yet for all its shiny optimism and liberal love-ins, The West Wing is smart, snappy and instantly engrossing. As a trauma-in-the-high-pressure-workplace, it operates in the same way as ER (with whom it shares an executive producer, John Wells), with engaging characters emerging from tumultuous camera work, the spaghetti of multiple plot lines, and sparky, speedy dialogue. It verges on the corny at points - especially when Sheen's Bartlet is spinning some folksy story with a Moral - and its theme tune is awfully turgid, but The West Wing succeeds by focusing less on Bartlet and more on those around him. The West Wing may not enchant audiences here quite like it has in the States, but it's undoubtedly must-see TV.

How's that for shiny optimism?

Only six minutes into The West Wing (Channel 4) and the blood is pumping, the adrenaline is flowing and the drama is racing along at full tilt towards a season finale cliffhanger so tense and gripping your fingernails ache and your spine tingles. What's more, there's some terribly apposite political comment thrown in for good measure.

God bless judicious timing. In what is a first for Channel 4 - which has shunted The West Wing around the schedules like a date in Jeffrey Archer's diary - the last episode of this invariably classy series couldn't have appeared at a more auspicious moment, injecting badly needed political drama into an otherwise bland night on the box.

Even The West Wing's occasional dalliances with sentimental hokeyness can be forgiven as it is quick to undermine itself. (After President Bartlet chirps "Hey Steve, hey Mikey" on his way to a briefing, he cheekily asks his aide "Did I get any of their names right?" to which the aide replies "No, but you were close with a few.")

Aside from the fact that The West Wing is a liberal's wet dream with everyone on the White House staff a decent individual who believes in what they are doing - and even the sly veep having a good side - the confidence of the show is probably its most alluring attribute.

That writer and creator Aaron Sorkin started off this episode with nearly the end of the story and then flashed back 12 hours, a device normally reserved for Star Trek plots involving alternative timelines, is further testament (if any more were needed) that he is a skilled and bold dramatist and a man who doesn't underestimate his audience. There are few British television writers who would endeavour something so audacious, fewer who would pull it off and even fewer drama executives brave enough to let them try.

By replaying the action up to - and then beyond - what we know happened, Sorkin takes the drama to dizzying heights and, rather than giving you an excuse to nip out to put the kettle on, since it's the denoument that matters, the knowledge of events foretold (but not resolved) keeps you glued to your chair. As the cameras pull back from the scene of the attempted (successful?) assassination, with characters we have grown to love over the last five months sprawled on the tarmac and the words "People down. People down. Who's been hit? Who's been hit?" echoing out, The West Wing leaves you both enormously satisfied and hungry for more. Smashing.

The West Wing had a sad outing last time round on British TV. The first series began to be put further and further back in the listings by Channel 4, until it was on at 11pm and only attracting about a million viewers, whence it went digital. Channel 4's unwillingness to trust the viewing public to watch a fast-moving, difficult series on politics, rich with intercut conversations and complex asides on constitutional dialetic, was the opposite stance to that taken in America by producers NBC, who were rewarded for sticking with it when it picked up a record number of Emmys: Martin Sheen's fictional President Josiah Bartlet actually began topping semi-serious polls a couple of years back with voters fed up at the choice between Bush and Gore.

The series was gripping, witty, addictive, and the single reason I finally succumbed and got digital TV last year. And, if the first series was impressive, the second leave even that standing. The opener's a belter. It covers the aftermath of the President's shooting; and from the moment the hospital charge-nurse screams "Blue! Blue!", signalling the code for the prez's arrival, you'll be glued. He survives, you might as well know: but there are doubts about the chances of one of his team, which lets the writers deal for the first time, through flashbacks, with the way in which they all got together in the forst place. Much in genuinely moving, and there truly has to be genius at work somewhere when a lump can be brought to the throat during a scene in Nashua, New Hampshire, in which the topic of discussion is the New England dairy farming contract. It's a year now since I first watched this episode, and I found myself anticipating remembered tics, looks, phrases and reactions seconds before they took place, which is always a sign of the very best films.. There is, in later episodes, perhaps a little too much mawkishness, and there was a disasterous attempt to engage with reality by speed-writing an 11 September special, but in general the second series just goes on getting better.

There's also an eerily prescient little bit, in tonight's episode, when they worry that the shooting may have been the work of foreign terrorists, and the National Security Advisor tells her team: "At the moment we do not know the whereabouts of about half a dozen cell leaders, including bin Laden."

What Donna didn't know was that something drops from the sky once every 10 days with few - if any - repercussions. Donna also didn't know that CJ gets a similar fax issuing similar warnings every week and, due to the lack of repercussive impacts, CJ ignores it. She didn't know because Josh, her boss, didn't tell her for he thought it would be amusing for Donna to worry. It was.

But the Chinese satellite was simply a distraction. What was plummeting towards the earth at an alarming rate - darkening the sky, eclipsing the sun, emitting the low whistle of a heavy object's unimpeded downward trajectory - was a great big metaphor. With issues of full disclosure and committing fraud against the public amounting to the real possibility that all our White House favourites are accessories to a federal crime, and Oliver Platt turning up as a charmingly charmless White House counsel who duelled with both CJ and the First Lady (a brave or foolish man, to be sure), the satellite was the least of the West Wingers' worries. President Bartlet has multiple sclerosis and the shelf-life of its secrecy was fast running out.

In one of those exquisite West Wing moments which rewards your attention, flatters your intelligence and generally makes you feel all smug for keeping up, CJ - as the apex of one of Allison Janney's finest performances - delivers lines to give you goosebumps. "You guys are like Butch and Sundance peering over the edge of a cliff to the boulder-filled rapids 300 feet below thinking you better not jump 'cause there's a chance you might drown. The President has this disease and has been lying about it and you're concerned that the polling might make us look bad? It's the fall that's going to kill you." As close to genius as it gets in TV drama.

(The wrong tape was delivered to the critic which resulted in the above review for The Fall's Gonna Kill You being published 6 days before it actually aired).

Everything about this cliff-hanging episode was vintage West Wing, right down to the statistics about poverty (Rightwing, bad. Leftwing, good!), the stretched out metaphors and the emotionally over-egged scenes at Bartlet's make-or-break press conference. All of which is forgivable, of course, because the drama is so energetic, smart and engaging. (I'm not so sure about the inspirational power chords courtesy of Dire Straits, though.) Bartlet is still the Potus with the mostest and, given a choice of First Ladies, I'd have Abby over Sherry Palmer any day.