The conventional wisdom in this radically unconventional presidential race is that the voters have to get to know Barack Obama better. That's what this week's overseas trip was about: to showcase the senator as a potential commander in chief and leader of U.S. foreign policy.

    According to this way of thinking, as voters see more of Mr. Obama and become more comfortable with him (assuming no major foul-ups along the way), his chances of getting elected will be enhanced.

    Maybe so. But what about the other guy? How much do voters really know about John McCain?

    Senator McCain crossed a line that he shouldn't have this week when he said that Mr. Obama "would rather lose a war in order to win a political campaign." It was a lousy comment, tantamount to calling Mr. Obama a traitor, and Senator McCain should apologize for it.

    But what we've learned over the years is that Mr. McCain is one of those guys who never has to pay much of a price for his missteps and foul-ups and bad behavior. Can you imagine the firestorm of outrage and criticism that would have descended on Senator Obama if he had made the kind of factual mistakes that John McCain has repeatedly made in this campaign?

    (Or if Senator Obama had had the temerity to even remotely suggest that John McCain would consider being disloyal to his country for political reasons?)

    We have a monumental double standard here. Mr. McCain has had trouble in his public comments distinguishing Sunnis from Shiites and had to be corrected in one stunningly embarrassing moment by his good friend Joe Lieberman. He has referred to a Iraq-Pakistan border when the two countries do not share a border.

    He declared on CBS that Iraq was the first major conflict after 9/11, apparently forgetting - at least for the moment - about the war in Afghanistan. In that same interview, he credited the so-called surge of U.S. forces in Iraq with bringing about the Anbar Awakening, a movement in which thousands of Sunnis turned on insurgents. He was wrong. The awakening preceded the surge.

    More important than these endless gaffes are matters that give us glimpses of the fundamental makeup of the man. A celebrated warrior as a young man, he has always believed that the war in Iraq can (and must) be won. As the author Elizabeth Drew has written: "He didn't seem to seriously consider the huge costs of the war: financial, personal, diplomatic and to the reputation of the United States around the world."

    He also felt we could have, and should have, won the war in Vietnam. "We lost in Vietnam," said Mr. McCain in 2003, "because we lost the will to fight, because we did not understand the nature of the war we were fighting and because we limited the tools at our disposal."

    The spirit of the warrior was on display in the famous incident in which Mr. McCain, with the insouciance of a veteran bomber pilot, sang "Bomb-bomb Iran" to the tune of "Barbara Ann" by the Beach Boys.

    No big deal. Just John being John.

    But then, we are already bogged down in two wars. And John is running for president. It's hardly crazy to wonder.

    Part of the makeup of the man - apparently a significant part, according to many close observers - is his outsized temper. Mr. McCain's temperament has long been a subject of fascination in Washington, and for some a matter of concern. He can be a nasty piece of work. (Truly nasty. He once told an extremely cruel joke about Chelsea Clinton - too cruel to repeat here.)

    If the McCain gaffes seem endless, so do the tales about his angry, profanity-laced eruptions. Senator Thad Cochran, a Mississippi Republican, said of Mr. McCain: "The thought of his being president sends a cold chill down my spine."

    Senator Pete Domenici, a New Mexico Republican, told Newsweek in 2000: "I decided I didn't want this guy anywhere near a trigger."

    Both senators have since endorsed Senator McCain's presidential bid, but their initial complaints were part of a much larger constellation of concerns about the way Mr. McCain tends to treat people with whom he disagrees, and his frequently belligerent my-way-or-the-highway attitude.

    Senator McCain has acknowledged on various occasions that he has a short fuse and has at times made jokes about it. He told Larry King in 2006: "My anger did not help my campaign ... People don't like angry candidates very much."

    My guess is that most voters don't see John McCain as an angry candidate, despite several very public lapses. The mythical John McCain is an affable, straight-talking, moderately conservative war hero who is an expert on foreign policy.

    Barack Obama is not the only candidate the voters need to know more about.