John McCain likes Barack Obama. He admires and respects Obama. He believes Obama is "very impressive, he's thoughtful, he's centrist." Obama has "probably got a great future." He is "a very honest and fine person" — "absolutely" qualified to be president.

How do we know McCain feels this way? Because he said so, in public comments ranging from 2005 to as recently as May. And as the McCain campaign grew uglier last week — casting Obama as dangerous, dishonest and un-American — it was tempting to imagine the campaign McCain might have waged if he had based it on the respect for his opponent, and for the process, that he had long professed.

Last week, for example, McCain was angrily promising to "name the names" of those who caused the nation's worst financial crisis in decades. He was blaming Obama and his "cronies," and the "corruption" that Obama had "abetted" in Washington. Meanwhile, almost as if there were no meltdown, his running mate remained stuck on attacking Obama for "palling around with terrorists."

But imagine if McCain had selected for his running mate not a partisan attack dog but someone with deep knowledge of the economy and a record of reaching across the aisle.

Imagine if McCain himself had decided to respond to this crisis as an American first, a candidate second. "Yes," he might have said, "Democrats contributed to our problems with their lobbyist-fueled defense of Fannie and Freddie. But let's not pretend that Alan Greenspan, Phil Gramm, George W. Bush — and John McCain — weren't part of this, too. Warren Buffett saw this coming, but not many of the rest of us did. Let's postpone the recriminations and work together to fix this thing."

Last week, McCain was asking darkly, "Who is the real Senator Obama?" Imagine, instead, if he had followed his own advice from the spring, when he repudiated a state party attack ad that he said "distracts us from the very real differences we have with the Democrats." Imagine if he were challenging Obama on those policy differences.

I'm sure, in the crazed intensity of a presidential campaign, it's easy to start believing your consultants and television ads — believing that the other guy is dangerous and that only you can save the country. That must be especially true when the other guy is insulting you. The mud flies both ways in this campaign, with Obama and his allies relentlessly pounding McCain as out of touch, erratic, dishonest and, over and over again, dishonorable.

And honor is at the core of McCain's self-image. He's been running for president, more on than off, for almost a decade, but his determination hasn't had much to do with a highly defined ideology, program or set of policies. What underlies his ambition are values: service, patriotism, duty, honor.

It may be that it's easier for such a campaign to get blown off course. In an exceptionally pro-Democratic year, against an exceptionally unflappable opponent, it's not surprising that a campaign without bedrock policy goals would try first one thing, then another, with one of those things being character assassination.

I certainly can't prove that a McCain campaign built on respect and attention to issues would be faring better than the real thing. Without Sarah Palin to rally the base, and without the insidious questioning of Obama's patriotism, McCain might be even further behind.

But he also might be doing better — and he might be happier, too. That, at least, is one way to interpret an intriguing exchange that took place at a rally in Minnesota on Friday.

A woman took the microphone to say that Obama could not be trusted because he is an "Arab" — not a surprising misconception, given the Republicans who have taken to stressing Obama's middle name, Hussein. But McCain rebuked her: "No, ma'am, he's a decent family man, a citizen, who I just happen to have disagreements with on fundamental issues. And that's what this campaign is all about."

It's not what this campaign is all about, and as McCain was speaking, his campaign ads were calling Obama a liar. But it's what the campaign could have been about, if McCain had really wanted it that way.

Fred Hiatt is The Washington Post's editorial page editor.