The contradiction at the core of this week's Republican convention is that it has celebrated most lavishly the attributes of John McCain that previously provoked the most antagonism in the party he now leads.

Cheers have greeted every mention of McCain's willingness to work with Democrats, his capacity to disagree with leaders from his own party and his determination to steer his own course. None of that won much applause from conservatives and many party regulars last year when they were resisting McCain in the GOP presidential nomination race. And it's not clear that most Republicans would find those same qualities nearly as admirable next year if McCain wins in November.

The convention -- which culminated in a prosaic acceptance speech from McCain on Thursday that portrayed political reform and renewal as a patriotic duty -- has become a testimonial to McCain's independence precisely because McCain needs independent voters to win. In 2004, George W. Bush won reelection mostly by mobilizing his base; he became the first Republican in the modern polling era to win the White House while losing independent voters.

But Bush's strategy isn't available to McCain. Largely because of widespread disillusionment with the president, Democrats now enjoy their widest advantage in partisan identification over Republicans in decades. In 2004, Republicans equaled Democrats as a share of vote. In 2008, both sides agree, Democrats will outnumber Republicans, perhaps significantly, on Election Day. That means McCain can win only if he wins independents and a sizable chunk of crossover Democrats. Hence the convention's relentless focus on painting McCain as a maverick who elevates the national interest over partisan interest (not to mention the decision to provide Bush less time on stage than it takes to boil a pot of pasta).

The most immediate question raised by this portrait of McCain is whether it still applies. McCain can legitimately say he's taken the risk of breaking with his party to build bipartisan coalitions on tough issues such as immigration and judicial appointments more often than Barack Obama, whose collaborations with Senate Republicans have come mostly on less controversial questions.

But through this campaign McCain has transformed into a more conventional Republican. He's embraced the Bush tax cuts he once opposed, devised a health care plan that largely tracks Bush's, and renounced his own immigration bill. He's echoed the Republican call for more offshore drilling (after long opposing it) and, judging by the exuberant speech from running mate Sarah Palin, seems en route to reversing his opposition to drilling in the Arctic National Wildlife Refuge, too. In choosing Palin over the other vice-presidential possibilities that most intrigued him -- Sen. Joe Lieberman and former Pennsylvania Gov. Tom Ridge, each of whom supports legalized abortion -- McCain deferred to the social conservatives central to the modern GOP coalition. Voters who choose McCain in November will be picking a president whose personal ideology places him near Bush on most major issues.

That doesn't guarantee McCain would govern like Bush, though. Ideology is where a president starts; temperament is where he ends. Ronald Reagan was deeply conservative in ideology, but by temperament he was a deal-maker. Bush has been conservative and rigid. McCain is probably less ideological than either, but his temperament isn't easy to categorize. Often flexible, he also can be as unmoving as Bush at his most rigid. "John McCain basically has two modes of operation," notes Rep. Roy Blunt, R-Mo., the House Republican whip.

No one can say which of those modes would dominate a McCain presidency if he wins. If McCain is elected, he's virtually assured to face a Democratic Congress, probably with increased majorities. On some issues, like taxes, he might treat them as a foil by refusing to bend. But the only way he could fulfill his pledge to break gridlock would be to reach agreements with Democrats. Inevitably that would require concessions resisted by many Republicans.

That probably would be a lot less popular with Republicans than this week's cheers to McCain's "maverick" nature imply. The modern GOP is more ideologically uniform both in its electoral coalition and congressional representation than the Democrats and more committed to enforcing party discipline. For campaign reasons, the convention is highlighting the ways in which McCain has flouted that consensus. But a President McCain would face far more pressure for conformity from grassroots and congressional Republicans than candidate McCain. Swing voters drawn to McCain for his independence this fall are betting that as president he would repeatedly disappoint the activists who have most fervently cheered him in Minneapolis.

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