It is often said that Democrats fall in love with their nominee, but Republicans fall in line. Yet for the first time in modern memory, the Republican Party has had trouble picking one. As one scholar has pointed out, between 1952 and 2004, only one election (1964) did not contain a Nixon, Bush or Dole on the ballot. But this election is unique and difficult for the Republicans: An unpopular president waging an unpopular war and a party fresh off a roundhouse kick to the face in the 2006 midterm elections.

The very early frontrunner for the nomination was John McCain, who had evolved from a maverick in 2000 to a steadfast Bush supporter in 2004. He was thought to be the pick of the Bush White House and the political establishment. Then McCain’s candidacy imploded with poor fundraising numbers, which necessitated that he fire most of his staff.

Sometime around then, Rudy Giuliani took over, despite concerns about his pro-choice and pro-gay positions. But his obvious inability to compete in Iowa or New Hampshire (he came in sixth in the former and fourth in the latter) means he has to wait until Florida three weeks from now to even have a chance at the nomination.

Fred Thompson had his moment too, leading in the polls as soon as he entered the race (much later than the other candidates), but his support began to drop immediately thereafter. He was barely able to piece together a third-place finish in an Iowa race uncontested by Giuliani and McCain. Romney then picked up where Giuliani couldn’t, leading in Iowa and New Hampshire polls. But Romney’s attempt to balance business conservatives and evangelicals failed, and he finished second in both Iowa and New Hampshire. Mike Huckabee won Iowa but had no chance in New Hampshire, and seems to alienate enough people that he’ll never gain enough support in the big Feb. 5 states to have a serious chance.

The inability of any candidate to overcome his flaws and rise to the nomination poses a serious problem for the Republican Party. The Democrats are good at picking a nominee at the last minute and still competing (Bill Clinton didn’t win Iowa or New Hampshire), but it is unclear whether the Republicans can survive a vicious succession of primaries and unite in time for the fall campaign season. While the Democratic Party seems to have settled on Barack Obama or Hillary Clinton as likely nominees, the Republican fight will carry on for some time.

This will drain Republicans of resources, further divide the party into ideological camps (business types versus evangelicals, moderates versus hardliners, neoconservatives versus paleoconservatives) and likely, alienate enough voters that a pillar of the base doesn’t turn out, and the Democrats win.

One of the advantages of the Republicans in presidential races has been their willingness to fall into line. The party establishment picks a nominee, all of the factions unite behind him, and the party moves forward, organized and united, while the Democrats bicker and procrastinate on picking a nominee. It should also be noted that Republicans have won five of the last seven presidential elections.

The conventional wisdom is that the party is going to have to hold its nose and nominate John McCain, as he might be the one least tainted by early-state defeats or, in Giuliani’s case, not even bothering to compete. McCain’s problem is immigration: He supported President Bush on comprehensive immigration reform. Huckabee and Romney, meanwhile, step all over themselves, trying to sound as anti-immigrant as possible despite their ambivalent records. Several of the fringe candidates such as Duncan Hunter and Tom Tancredo ran as essentially single-issue candidates on immigration. Anything even approaching amnesty is anathema to the party base. McCain is lucky, however, that the issue has faded from the public consciousness (it brought about his decline from frontrunner to fourth place during the summer).

It’s unclear whether McCain would stand a chance against Obama in a national race, but he seems to be the GOP’s best bet. He would offer a stark contrast: a principled, experienced senator and veteran, hawkish on foreign policy, versus the gauzy, fresh-faced and ambitious Obama. He’s been mostly, though not entirely, consistent in his policy positions over the years, something that is strangely important to the American people. It would be a generational battle that shapes the political agenda for the decade following the conclusion of the Bush Administration.