It's a truism in the study of politics in the Third World that the real test of democracy is not voting a president in but voting him (and his party and/or relatives) out.
That's true in the First World, too. For example, I was a little surprised in 1981 that The Economist was relatively enthusiastic that in the French election that year the Socialist Mitterand had taken power from the Gaullist Giscard d'Estaing and immediately set about soaking the rich. But, the magazine pointed out, the last time there had been a substantive change of power in France was in 1958 when de Gaulle came to office and that was during the mutiny of the French Army in Algeria, which had seized Corsica and was threatening to seize Paris. So, the defeat of the Gaullists and their good grace in accepting that defeat by, you know, leaving office marked a milestone in the maturation of French politics.
The election of Barack Obama in 2008 as the first black president of the United States was widely celebrated as marking a step forward in American history. But nobody gave much thought at the time about whether large swathes of American voters and elites are mature enough to accept with good grace another step forward: a black man being voted out of the White House.
The weird, hypersensitive frenzy that has entered American political life since Mitt Romney wrapped up the GOP nomination and the fall campaign began in earnest suggests that many people on the left of center would perceive Obama losing in 2012 not as just one of those things that happens in a democracy, as George H.W. Bush and Jimmy Carter can attest, but as a Giant Diss to blacks. This potential Triumph of Racism (as they perceive it in their Who-Whom worldview) would be intolerable, so saying almost anything to ward off Obama's defeat in November is morally justifiable.