Less than two years ago, Barack Obama was sworn in as president amidst proclamations of a partisan realignment. But in this falls midterms, scores of his fellow Democrats lost their jobs. The best evidence suggests that Obamas signature accomplishmentpassage of a healthcare reform bill that had long eluded progressivesplayed a key role in the historic defeat. It also highlighted the delicacy of partisan regimes, particularly those prematurely designated as realignments by academic or popular observers.