Follow McCain's candidacy in photographs.
In a presidential election year in which a black man and a white woman are each staging historic candidacies, John McCain — the maverick Republican — may be the most radical party nominee.
While both New York Sen. Hillary Clinton and Illinois Sen. Barack Obama are making unprecedented bids for the Democratic nomination, both are also orthodox party members who deviate very little from the mainstream. The same can't be said for McCain, the presumptive GOP nominee.
As fellow Republican and former House Speaker Newt Gingrich sums it up: "John McCain couldn't be a status quo person if his life depended on it."
Gingrich knows something about boom-and-bust cycles in politics. Right now with the Republican Party in retreat, he thinks McCain might be just the change the party needs.
"McCain may turn out to be a surprisingly timely break in what would otherwise have been, I think, a Republican disaster," Gingrich said. "His willingness to do what he believes in, and not care about the political conventions will certainly break up both the pattern of domination by the regular Republican establishment and the pattern of movement conservatives defining the party."
McCain won the nomination in spite of opposition from large wings of the Republican establishment and the conservative base. Sen. Lindsey Graham (R-SC), one of McCain's closest allies in the Senate, says McCain could now have a profound effect on his party.
"There's aspects of John McCain's philosophy as a Republican that will tie us back to those principles that really made the party different from Democrats, and there's also an aspect of John McCain that will take the party in a new direction: global climate change, campaign finance reform, immigration reform, issues that present a new ideology. That we ought to be embracing Democrats, that it's not a crime in the McCain Republican Party to work with Democrats for the greater good," Graham said.
McCain himself wears his bipartisan credentials on his sleeve.
After the March 4 primaries, he said, "The American people's patience is at an end for politicians who value ambition over principle, and for partisanship that is less a contest of ideas than an uncivil brawl over the spoils of power."
"McCainism," out of necessity, could be a rejection of the hyper-partisanship of President Bush's approach to governing and Karl Rove's approach to winning elections. As a president, McCain could not expect to govern without a lot of Democratic support in Congress. As a candidate, McCain could not win the White House without the votes of independent and swing voters.
Gingrich says that McCain is determined to figure out how to have a governing coalition that encompasses about 60 percent of the country.
"He understands that the red-versus-blue base mobilization is crazy in the long run. It works for one election. Then it is destructive," he said.
In 1992, former President Bill Clinton called himself a "new Democrat" when he wanted to move his party to the center. In 2000, Bush called himself a "compassionate conservative" when he wanted to break with the hard edge of the Gingrich revolution.
There is no slogan yet for McCain's brand of conservatism. But his supporters describe him as a Republican reformer ready to tackle campaign finance, immigration, entitlements, earmarks and the tax code. And they say that he would also try to appeal to a group of swing voters who have been hard for more traditional Republican candidates to reach: the suburban working-class, or as Minnesota Gov. Tim Pawlenty calls them, the "Sam's Club Republicans" — as opposed to "country club" Republicans.
Sam's Club voters, Pawlenty says, care about getting their children a good education and a shot at a better life — without being overburdened with taxes.
"They're interested in school funding and reform, and they're worried about health care costs," Pawlenty says. "And they want to know, without having the government take it over, can you do something to help them make health care more affordable. And on each of those, John McCain has spoken pretty strongly in ways that I think would be attractive to a Sam's Club Republican."
When it comes to bread-and-butter issues, the Democrats have a long-standing advantage. McCain's supporters say in the next six months, he must unveil his own agenda on the mortgage market crisis, the economy and energy.
Michael Gerson is a former Bush speechwriter and a McCain admirer who says McCain will need to focus more on domestic issues.
"The major criticism of John McCain you hear among colleagues on Capitol Hill and others is that he is engaged on the international front. He is not particularly intellectually engaged on this domestic front, and he is going to need to be in this election, because we've moved from an international focus to a much more domestic focus," he said.
Others are even more skeptical for different reasons.
Bill Galston, a former Clinton White House domestic policy aide and a supporter of Hillary Clinton, says the question is whether McCain can be a Theodore Roosevelt for the 21st century.
"And the answer is, it would depend on which President McCain showed up the day after his inauguration. Because his campaign right now is a promiscuous heap of ideas that will not cohere in one administration," Galston says. "Does he represent a departure from encrusted Republican orthodoxy? And the answer is yes, absolutely. But then you can ask a different set of questions."
Galston says despite McCain's break with his party on a long list of issues — from climate change to torture — the task of moving the GOP in his direction will be next to impossible.
McCain's task will be even harder this year. He will try to chart a new path for Republicans in a campaign where the Democrats will be spending all of their energy trying to frame him as nothing more than a carbon copy of Bush.