The Democrats were deciding which historic nominee excited them most. Republicans can't decide who depresses them least.

Asked if they're worried by the extended primary contest between Mitt Romney and Rick Santorum, a lot of Republicans are playing it cool. Said Senator Mitch McConnell, "It's reminiscent of the contest between Obama and Clinton. That didn't seem to have done Democrats any harm in the general election, and I don't think this contest is going to do us any harm either."

But the GOP contest is actually very different from Obama versus Clinton. In 2008, there was no incumbent. Insofar as progressives demanded that a candidate take a position to prove his or her bona fides, it was opposition to the Iraq War, which a majority of Americans had already turned against. On health care, Obama opposed an individual mandate, calculating that he'd benefit from a more centrist position. What else separated the pols? Clinton argued that she had more experience and was better prepared to take a "3 a.m phone call;" Obama retorted that his judgment was superior, as evidenced by his early opposition to the Iraq War. The two also disagreed about the nature of Washington, D.C. Obama argued that fundamentally reforming the system was a prerequisite for the substantive changes he desired, whereas Clinton argued that realism demanded working within the system, and that she'd excel at doing so.

These matters weren't deal-breakers.

In contrast, Romney and Santorum are proving their bona fides to conservatives by invoking positions and rhetoric likely to hurt them in a general election, whether it's the former talking about how he is "severely conservative," or the latter insisting contraception isn't okay, even if it should remain legal. Neither candidate has a base of supporters anywhere near as sizable or enthusiastic as Obama or Clinton. Perhaps most importantly, neither Clinton nor Obama were insisting that their opponent was a fraud and a phony. Insofar as Romney and Santorum are accurate in their attacks, it is a deal-breaker for some Republicans.

Thus the counter-narrative, as articulated by John Heilemann:

...the Democratic tussle in 2008, which featured two undisputed heavyweights with few ideological discrepancies between them, may be an exception that proves the rule. Certainly Republican history suggests as much: Think of 1964 and the scrap between the forces aligned with Barry Goldwater and Nelson Rockefeller, or 1976, between backers of Gerald Ford and Ronald Reagan. On both occasions, the result was identical: a party disunited, a nominee debilitated, a general election down the crapper.

With such precedents in mind, many Republicans are already looking past 2012. If either Romney or Santorum gains the nomination and then falls before Obama, flubbing an election that just months ago seemed eminently winnable, it will unleash a GOP apocalypse on November 7--followed by an epic struggle between the regulars and red-hots to refashion the party. And make no mistake: A loss is what the GOP's political class now expects.

In related news, betting on an Obama victory is getting more expensive on InTrade:

We're still early in Election 2012. Anything could happen. But Republicans shouldn't comfort themselves by looking to 2008 as a precedent for their eventual victory. The necessary parallels just aren't there.