The 2012 election is shaping up to be more polarized along racial lines than any presidential contest since 1988, with President Obama lagging behind Republican Mitt Romney among white voters by 21 percentage points, a steep drop in support from four years ago.

As he did in 2008, Obama gets overwhelming support from non-whites, who made up a record high proportion of the overall electorate four years ago. In that contest, 80 percent of all non-whites supported Obama, including 95 percent of black voters, according to the exit poll. In the Washington Post-ABC News national tracking poll released Wednesday, Obama wins 79 percent of non-whites, and support for his reelection is nearly universal among African Americans.

But among whites, Obama is currently doing much worse than he did in 2008. At this stage four years ago, Obama trailed Republican John McCain by eight percentage points among white voters. Even in victory, Obama ended up losing white voters by 12 percentage points. […]