A new NBC News/Wall Street Journal poll illustrates a racial polarization in the electorate that poses challenges for both candidates.

The poll showed Mitt Romney earning zero percent among blacks, compared to Obama’s 94 percent. And Romney trails among Hispanics by a margin of 63 to 28 to the president.

But Obama, who earned 43 percent of the white vote in 2008, is down to 40 percent now, according to the survey. And other polls have shown him hovering in the 38 percent range, a number that would make it very hard for him to win reelection.

These numbers explain both campaigns’ strategies. The Democrats’ intense focus on the controversial abortion comments of Rep. Todd Akin, the GOP’s candidate for the Senate seat in Missouri, could help them win white women, who favor Republicans slightly in most polls but are in some ways the swing voters of this election. The NBC poll showed Romney ahead by 19 points among white men, but only 8 among white women. (In 2010, when Republicans made huge gains, they won the white vote by 23 points, including white women by 19.)

Romney, on the other hand, has spent little time or money courting blacks or Hispanics after taking strongly anti-illegal immigration stands during the GOP primary.