George Clooney takes his politics very seriously, but his great talent is that he can sell it all as a bit of a hoot. He turned his charm on Stephanie Bunbury.

Just before the US invasion of Iraq got under way, one of the local news magazines featured 10 Hollywood actors on the cover, including the exceedingly agreeable George Clooney. "Traitors!" shrieked the headline. Clooney, it was clear, was not going to have a good war, at least not on the home front.

"I was getting hammered by the press pretty good," Clooney recalls with some relish. He was on television next, the subject of a talk show that said his career was finished thanks to his disloyalty. If you want to pick on a turncoat, you can't do better than a white one. "That Dr Ross seemed so nice in ER," you imagine the viewers sighing. "Who would have guessed he was so filthy pink underneath?"

Everyone knows now, of course. In the US, 44-year-old Clooney is as famous a liberal as he is a heart-throb. That was Clooney in Berlin, using his time at the film festival there to march in the protest against the Iraq war; that was him marching the following week in London. He just will not keep his head down. Just recently, there was Clooney again at the G8 convention, in a huddle with Bono and Bob Geldof, talking about debt.

And now, here's Clooney ruffling the hawks' feathers with a film about Senator Joe McCarthy, the infamous communist witch-hunter who did as much as anyone to fan the fires of the Cold War. At a time when America was collectively terrified that the Russians were coming, McCarthy made his name persecuting supposed communists through the secret findings of the House Un-American Activities Committee.

The central figure in Good Night, and Good Luck, however, is not McCarthy but the crusading journalist Ed Murrow, who gave a voice to a liberal opposition so cowed that it seemed to have vanished entirely. Murrow was a television commentator on CBS who, every week, gave his views on the news from behind a pall of cigarette smoke, his clipped and even delivery sounding as a clarion call of reason. He was a great hero of Clooney's father, Nick, who was himself a television commentator and news producer and whose own liberal convictions, says Clooney jnr, cost him several jobs during the McCarthy era.

"He got in a lot of trouble over the years and we moved around a lot, but that's kind of the fun of it," he says now. "I remember being a kid and saying to my dad, you know, 'Maybe for once just shut up and don't say anything and we could finish eating a meal before we get kicked out of a restaurant'. Now I'm very proud of getting kicked out of those restaurants."

What was important, his father advised him during the Iraq protests, was that he could look back and feel he'd been on the right side of history. In the meantime, it didn't matter if the mud stuck. Around the same time, George dug out some of the Murrow homilies his father had read so avidly for some timely inspiration. "I remember reading lines like 'We will not confuse dissent with disloyalty' and 'Remember that we are not descended from fearful men', and I thought that those were interesting parallels," he says. "We go through these periods of fear - you know, planes fly into buildings in New York - and suddenly you are unpatriotic if you question other aspects of your government."

Moreover, he saw that in the light of current terrors, McCarthy's reputation as a twisted aberration of history was being reconsidered. It is a good time to look once more at the facts, he insists. Murrow, for instance, never said that those accused by McCarthy were not communists. He certainly never dared to say that Americans had every right to be communists under a democracy that upheld freedom of speech. Nobody would have said that then, says Clooney. "Even the best, hardcore journalists weren't doing that. They weren't saying, 'Hey, on top of everything else, you can be a communist' - and remember, half of them had certainly been to parties if nothing else 15 years earlier, because we were all on the same side then. But I don't think anyone brought it up and we were trying to keep this (movie) historically accurate."

What Murrow said was simply that the accused should be able to face their accusers. "That you cannot just throw people in jail without a lawyer. And that's what I see happening now. Those guys may very well be terrorists in Guantanamo Bay, but either they are war criminals and they get rights under the Geneva Convention, or they are criminals and they have the right to a lawyer. And if not, what is the country we are defending?"

Clooney's particular gift is that he can deliver speeches like this without losing that killer smile, speaking quickly and softly while looking you straight in the eye. You feel, if not exactly like his mate, at least like a co-conspirator. More amazingly, he can do the same thing to a roomful of people. Most of all, however, there is always a sense with Clooney that, at any moment, he might break out the bunny ears and dance around the room. That whatever he's doing, it's a whole bunch of fun.

The Clooney lifestyle is certainly geared to fun in a way that doesn't click at all with his status as Hollywood's pre-eminent worrywart. Unlike Sean Penn, another famous left-winger, he welcomes highly paid advertising jobs, lending his famous features to the promotion of prestige watches, cool sunglasses and goodness knows what else. Unlike Susan Sarandon and Tim Robbins, he doesn't aim to live like normal folks: his house next to Lake Como in Italy, as seen in Vanity Fair, looks like a hideaway fit for Bond.

The trappings of his fame, in fact, all lie somewhere between Bond and Hefner. He does the parties. He wears the suits. His love life is supposedly that of an unreconstructed Casanova, surrounded by innumerable, undifferentiated lovelies at all times. He is even building a casino in Las Vegas.

It is impossible to imagine Susan Sarandon or Tim Robbins wanting to go near a casino, let alone own one, even if they too were planning to donate a quarter of their takings to Make Poverty History. George Clooney, by contrast, is unambiguously a star of the old school. This is despite the fact that Ocean's Eleven is his only megastar-style hit apart from A Perfect Storm, a film that, as he says, "is about a big wave rather than me".

The triumph of the Clooney star persona is clearest in the press discussion of his films, which are invariably described as mainstream. The first film he directed was Confessions of a Dangerous Mind, a challenging, inconclusive story of a TV game show host who may or may not have been a spy. And there is nothing mainstream about Good Night, and Good Luck, a black-and-white film that meticulously describes a small political episode that took place more than 50 years ago. Clooney is in it, but he's almost unrecognisable behind glasses and acquired jowls, as television producer Fred Friendly. Murrow is played (with uncanny verisimilitude) by David Strathairn, an art house actor known chiefly for his work with maverick director John Sayles.

Nobody plays Senator McCarthy. His presence is suggested through the clever use of historical footage. "As George has said, if you had to hire an actor today to play Joseph R. McCarthy, no one would ever believe in him, because he would be too vaudevillian, too monstrous," says Strathairn. Like Murrow, who decided the best way to deal with McCarthy's politics of hate was to get him on air so people could hear what he was really like, Clooney wanted him to be a victim of his own words. It's not the sort of thing you find in a mainstream film, where they'd normally be going head to head.

Good Night, and Good Luck - named for Murrow's sign-off - has won several prizes at the Venice and New York film festivals, which is not surprising, but even the chatroom crowd, mostly teenagers with a weakness for action, are transfixed by it. The American reviews have been rapturous. "The most compelling American movie of the year so far," said Newsweek succinctly. The Village Voice saw it not only as a wake-up call to the modern media, but to a memory of civilised values. It depicts, wrote Michael Atkinson, "a more sophisticated yesteryear (that may be) something of an eye-opener for culturati born since the Nixon administration, for whom an anchorman who speaks in multiple clauses, who quotes from Shakespeare, and whose basic righteousness dictated his actions is as familiar as a politician with respect for his constituents".

Syriana, a thriller about intrigues in the oil industry and the first film by Traffic screenwriter Stephen Gaghan. Clooney plays real-life CIA agent Robert Baer, who wrote the book on which the film is based; controversially, the script parallels its account of intrigue at the big-money end of oil with a sympathetic view of a burgeoning terrorism in Pakistan. It has been screening in American cinemas for the past fortnight and seems to be attracting just as much enthusiasm as Good Night, and Good Luck. "It shakes us up and prompts us to question world policies," said USA Today. "We need more movies like this."

No wonder Clooney insists that the political tide is slowly turning in the US. "I've always had that political bent. I grew up with politics and journalism," he says. "Look, I like entertainments; I'm proud of Ocean's Eleven. But I also like being able to shake it up every once in a while and get in a little trouble."

Next up, he plans to remake the '70s classic Network, about a television station where an unhinged news anchorman is encouraged to kill himself on air because it will boost ratings. Clooney grew up around television - both his parents worked in it and as a small child he was often carted down to the station, where he would sit on the sidelines and observe. "Television was my babysitter. It is the world I know very well and am excited by and thrilled by and disappointed by at times, as I think all of us are." He is comfortable messing about with its behind-the-scenes stories.

One thing he won't be doing, however, is going into politics. His father Nick, who is now 71, ran for Congress in the last US election. George contributed to the campaign but stayed well away from it, judging that his profile would do the cause more harm than good. His dad still lost resoundingly. "They ran a mean campaign," says Clooney. "They had a picture of my dad - you know, my dad is very straitlaced - mocked up to show him smoking a joint. My dad has never smoked a joint in his life, but that's campaigns."

Clooney, by contrast, has said he would have to run a campaign on the basis that whatever it was, he did it: yes, he had sex with that person; yes, he took those drugs. But it won't happen. "I spent six months doing Failsafe in Washington with politicians, following them around," he says. "And even the politicians I really liked, I thought I would never do this in a million years. Too many deals you have to make. It's more fun directing."

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