This time I’ll give the answer first and explain it later: Groupthink.

Why did Mitt Romney’s campaign fall apart? Because no one believed him when he said he was conservative. Despite having made a living off of rescuing companies from debt and being one of the most economically conservative of the bunch, his socially liberal record as governor of Massachusetts was used against him in such a way as to paint him as a flip-flopper and panderer.

Romney prior to his campaign had been in the unfortunate position of having to choose between switching his positions on several issues mostly social in nature (gay marriage, abortion, etc.), and being unpalatable to the Republican party. Ultimately he chose the former, and while the latter probably would have worked even less well (just ask Rudy Giuliani), he still got hammered by Huckabee in several races he should have won, all else equal.

McCain was in much the same situation. With a reputation as a maverick who didn’t mind working with Democrats to push through certain bills and an unpopular (among Republicans) stance on immigration, it looked like McCain would suffer the same fate as Romney (or that he had suffered the same fate as Romney would, McCain’s collapse coming well before Romney’s). But McCain had a distinct advantage over Romney: as a war hero, people trust him far more than a businessman. He practically oozes trust, the reserves of which have yet to be depleted.

The groupthink of the Republican party was made evident in Huckabee’s victories in several Republican primaries. As the only viable candidate who could claim “conservative” values where the others lacked (namely in the social arena), people flocked to him in droves despite each of the others (with the possible exception of Fred Thompson) having far more credentials, experience, and substantiative ideas than he. But McCain, solely by virtue of his war hero status it seems, managed to pull out ahead.

What is baffling now is that only since his presumptive clinching of the nomination has he been most vocal about his conservatism. He has even switched convictions on several issues (Bush tax cuts, for example) in order to be more palatable to the Republicans, despite that same strategy being behind his campaign’s original collapse as well as Romney’s collapse. McCain’s strength is in his independence, not in toeing the party line, especially now that he already practically has the nomination. Espousing his conservatism can only damage him in the long run. Despite what Rush Limbaugh and Ann Coulter may say about him, when faced with the alternative - Obama or Clinton - even the most conservative McCain hater must eventually vote for him (unless, heaven forbid, Ron Paul keeps going as an independent). When sticking with one or two unpopular opinions (regardless of their wider popularity outside the party) makes a candidate so unpalatable as to force him to change them - especially completely irrelevant meta-issues such as party loyalty - it’s time to rework the way parties do business.

So McCain, keep flouting the Republican party, and for heaven’s sake stop whoring yourself out to a base with so many people who probably don’t even know what “conservative” means but will vote as long as you are one. Your strength is the independent base - embrace them, and keep thinking for yourself.