With the exception of the Fox News Channel, the liberal tilt of the mainstream media - the major newspapers, the networks, National Public Radio, the news magazines - has long been a fact of American life. No one observing the coverage of this year's presidential campaign with both eyes open can have much doubt that the media establishment is pulling heavily for the Democratic ticket.

That explains why, for example, the intense media interest in George W. Bush's National Guard records last February wasn't matched by an equally intense interest in John Kerry's Navy history in May, when the Swift Boat Veterans for Truth first went public with their criticisms. Far from leaping on the charges that Kerry's Vietnam heroism had been greatly exaggerated, the mainstream media's initial reaction was to largely ignore them. And while the press saw no reason to question the credibility of Bush's accusers or to demand that Kerry repudiate them, their attitude toward the Swift Boat vets has been much more hostile.

None of this should come as a surprise. The nation's newsrooms are Democratic strongholds, and that cannot help but affect their coverage of the news. Evan Thomas, the assistant managing editor of Newsweek, put it plainly last month.

"Let's talk a little media bias here," he said on the PBS program "Inside Washington" on July 11. "The media, I think, want Kerry to win. And I think they're going to portray Kerry and Edwards . . . as being young and dynamic and optimistic and all, there's going to be this glow about them that is going to be worth, collectively, the two of them, that's going to be worth maybe 15 points."

Just how lopsided is the pro-Kerry bias? When New York Times reporter John Tierney surveyed reporters covering the Democratic National Convention last month, the results were striking.

"We got anonymous answers from 153 journalists, about a third of them based in Washington," he wrote on Aug. 1. "When asked who would be a better president, the journalists from outside the Beltway picked Mr. Kerry 3 to 1, and the ones from Washington favored him 12 to 1. Those results jibe with previous surveys over the past two decades showing that journalists tend to be Democrats, especially the ones based in Washington. Some surveys have found that more than 80 percent of the Beltway press corps votes Democratic."

Of course, the proof of the pudding is in the tasting, and for tasting liberal bias in journalism, no one tops the Media Research Center. Founded by conservative activist Brent Bozell in 1987, the MRC has become an indispensable resource for anyone interested in how political attitudes shape news coverage. Its most illuminating technique is the simplest: It monitors journalists' words and quotes them. What it has found time and time again is a skew to the left: a tendency to celebrate, echo, or defend Democrats, liberals, and left-of-center ideas.

Consider the reporting at the Democratic convention. In its latest "Notable Quotables," the MRC serves up more than two dozen fawning quotes from journalists about the brilliance, wonder, and allure of the Democratic team. You can find the complete litany (plus detailed daily reports on the convention coverage) at www.MediaResearch.org, but these examples will give you a flavor of the whole:

I was standing next to the young speechwriter who worked with Kerry on this speech. . . . The look on his face: rhapsody throughout. I don't know how this was perceived at home. But here in the Massachusetts delegation, where I was standing, it was perceived very well.

- ABC's Dan Harris, following John Kerry's speech to the Democratic convention.

People who served with him in Vietnam said, You can't believe what he's like in battle. He just changes. He gets this look over him. And when I saw him walking down the aisle tonight on the way into the speech, I said, 'Oh yeah, there's that look.' And I just knew at that point that he's going to nail this, and he did. I have never seen the man speak so well.

- Time magazine's Joe Klein on CNN.

John Kerry working himself literally into a sweat. Or as my high school English teacher would prefer, into a high state of perspiration. An almost literal thunder inside the hall, shaking the Fleet Center in a way that it seldom shakes, if ever, even during a Celtics basketball playoff game or a Bruins hockey playoff game. These Democrats, as the speech built, having what amounted to maybe a three-thousand-gallon attack about every three minutes, united in a way the Democratic Party has not been for about half a century.

- CBS anchor Dan Rather.

For those who doubted John Kerry could pull off a stirring speech, doubts dispelled. For those who doubted John Kerry could unite a traditionally fractious party, doubts dispelled.

- ABC's Charles Gibson on "Good Morning America."

The personality that Edwards exudes when he comes to these events is something that's pretty infectious with these delegates. And I talked to one delegate yesterday who says, 'You know, I'm coming to like John Kerry, but I haven't yet fallen in love with him. But I will tell you this, I have fallen in love with John Edwards.' It's obvious the charisma out there gets to everybody here in the Fleet Center.

- CBS's John Roberts, after John Edwards finished his convention speech.

People talk about John Edwards being the sexiest politician in America. I think Teresa Heinz may be the sexiest spouse of a national candidate in my memory. She comes across pretty strong, soulful, tender even, in a way. So I think she had an effective performance.

- Wall Street Journal reporter John Harwood on CNN.

Don't expect next week's Republican convention in New York to inspire similarly starry-eyed adulation. As Newsweek's editor concedes, the media want Kerry to win. To be sure, most journalists are professionals who take seriously their obligation to be accurate and fair. But what is true for most people is true for journalists, too: When you want something badly enough, it shows.