If a third-party candidate could be elected president, John McCain would win in a heartbeat.

He would win even though many voters, especially Democrats and independents, disagree with some of his positions. Voters would still flock to McCain because he displays traits that are increasingly rare in the vicious atmosphere of Washington, and peculiar to the Republican senator from Arizona.

Call it “McCainism” – a kind of straightforward authenticity. McCain makes you feel a real person is speaking, who listens to you.

I believe there is a hunger for McCainism in blue states – and in red states, too. McCainism means you admit mistakes and don’t keep on pretending everything is rosy, especially in Iraq.

McCainism means you don’t denounce your critics as traitors, but hold a civil dialogue with them. It means an absence of arrogance, the ability to make self-deprecating jokes, to consider other opinions when your policies aren’t working.

Without a dose of McCainism, the White House will continue to lose support for its Iraq venture and fail to ward off disaster in the Middle East.

The difference between the Bush approach and McCainism was on full display in the president’s Veterans Day speech. Bush accused congressional critics of sending “the wrong signal to our troops and to an enemy that is questioning America’s will.”

How can President Bush trash his critics when he fails to take responsibility for administration mistakes that strengthened the enemy? Bush says Iraq is “the central front in the war against the terrorists,” but it wasn’t before we invaded.

Doesn’t the president understand how his constant stonewalling undermines support for his Iraq policy, rather than rallying the country? People aren’t blind. Administration obfuscation about the past makes Americans doubt White House predictions about Iraq’s future.

That’s why it’s so refreshing to hear McCain talk. Last week, at the conservative American Enterprise Institute, he answered questions on what went wrong in Iraq.

“Failure to anticipate and plan for postwar Iraq,” the senator said bluntly. “Failure to anticipate looting, put enough troops on the ground. Not enough interagency cooperation.”

McCain believes we must stay on in Iraq until Iraq has “a flawed but functioning democratic government” and Iraqis can police most of their country. But he insists: “Let’s not tell Americans everything is going great.” Once we admit our failures in Iraq, “the key is to fix them.”

That kind of frank talk from the White House could probably rally the country, since no one wants to see Iraq end in a disaster. Instead, the White House tries to shift the focus from its past errors by attacking critics of prewar intelligence.

Bush says two governmental studies found no evidence that prewar intelligence was twisted. But neither study assessed the central issue – whether the White House over-hyped the intelligence it was given. Republicans have blocked a promised Senate investigation of such questions.

McCainism takes a different approach. He rebuts those who say the president “lied” but stresses that it’s legitimate “to criticize and disagree and debate” administration policy. McCain understands Americans will only rally behind a leader who doesn’t appear to be hiding the facts.

The senator also understands that you can’t fight terror in the name of American values without ensuring the fight won’t undermine those values. McCain got the Senate to approve, by an amazing 90-9 vote, a prohibition on torture, cruel and inhumane treatment of terror suspects. Torture doesn’t work, says McCain, and is morally wrong.

The White House has threatened to veto any bill containing McCain’s anti-torture language. So why did the Republican-led Senate endorse McCain’s ideas?

Because many Republicans understand, as the White House does not, that they need a more forthright response to public skepticism about Iraq policy. Yesterday, Senate Republicans borrowed a chunk of Democrats’ language and passed a resolution calling for a clearer plan for ending the war in Iraq – although the language was mushy.

More than 60 percent of Americans now disapprove of the way Bush is handling Iraq. McCain understands why. Many Republican senators get it (though their party is unlikely to nominate a maverick like the Arizonan). But there’s no sign yet that President Bush gets it. And McCainism without McCain is probably a nonstarter.

Too bad third-party candidates can’t get elected in the United States.

– Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer.