Who's the real John McCain? That's a question both Democrats and Republicans are asking.

The McCain most familiar to voters is the "straight talker" who made a failed bid for the 2000 Republican presidential nomination. The straight-talk message was perfectly timed for that campaign because it defined McCain as the un-Clinton. President Clinton famously said, "I did not have sexual relations with that woman," "It depends on what the meaning of 'is' is," and "I didn't inhale"—the opposite of straight talk. McCain's message was the antidote.

But McCain also ran as a harsh critic of George W. Bush and his conservative base. "Governor Bush is a Pat Robertson Republican who will lose to Al Gore," McCain said in February 2000. McCain's campaign style defined him as a maverick moderate in the minds of many voters. Since then, McCain has stood up to President Bush on campaign finance legislation, embryonic-stem-cell research, a constitutional amendment to ban same-sex marriage, and, most dramatically, torture. On the Senate floor, McCain said, "This isn't about who they are," referring to the people being detained by the United States. "It's about who we are."

A Gallup Poll taken last year showed that Republicans and Democrats give McCain equally good marks. Among each party's members, he had a favorable rating of more than 2-to-1. Few political figures today enjoy popularity that cuts across party lines like that. In 2004, Democratic presidential nominee John Kerry even considered picking McCain as his running mate. McCain the maverick moderate seems to be perfectly positioned to become the un-Bush of 2008. He can offer something Bush promised in 2000 but failed to deliver, namely, to be a uniter not a divider.

But it wasn't McCain the maverick moderate who addressed a conference of Southern Republicans this month. It was McCain the partisan conservative, the steadfast Republican who sticks with Bush during tough times. McCain asked the delegates to write in Bush's name in the 2008 presidential straw poll, saying, "He's our president and the only one who needs our support today."

McCain defended Bush on the Dubai ports deal when other Republicans abandoned him. ("The president deserved better.") He agreed with Bush on the lost cause of overhauling Social Security. ("The president of the United States did exactly the right thing.")

McCain has also steadfastly supported the war in Iraq, saying, "I'll be glad to have an academic discussion as to whether we should have gone into Iraq or not. I still believe we should." He warns, "You read [Abu Musab al-]Zarqawi, you read bin Laden: We leave Iraq, they're coming right after us."

McCain's critics see naked political calculation behind the senator's actions. The Republican nomination is wide open for 2008, when McCain will turn 72. That's likely to be his last chance. Moreover, here are two unusual facts about the 2008 election. No. 1: This will be the first open presidential election since 1928 not to have a sitting vice president in the running. That leaves a vacancy for the role of Bush loyalist. McCain has been making connections with the Bush money network and the Bush campaign machine.

Is this a new McCain? Not really. There were glimpses of McCain the partisan conservative in 2000, when he said, "I am a pro-life, pro-family, fiscal conservative, and advocate of a strong defense." He strongly defended Bush's Iraq policy at the 2004 Republican National Convention, saying, "The mission was necessary, achievable, and noble." McCain the partisan conservative would be well positioned to win the 2008 nomination. Sure, conservatives distrust McCain, but they might go along if they see him as the only Republican contender who could defeat the dreaded Hillary Rodham Clinton.

If McCain wins the nomination, fact No. 2 would come into play: Not since 1952 has a presidential ballot lacked an incumbent president or vice president. So once McCain secured the GOP nomination, he would have no obligation to defend the Bush legacy. He could turn back into McCain the maverick moderate to try to win the general election by gaining the support of Bush-hating Democrats and independents, two groups who have lately become very critical of McCain.