Two sets of polls show that Barack Obama has leads of 20 points or more in Maryland and Virginia which vote Tuesday as part of the “Potomac Primary” that also includes the District of Columbia. One headline is that Obama is running about even with Clinton among white voters, which had not been true in many Super Tuesday polls. He retains his large edge among black voters.

For a good discussion of the Potomac Primary and other upcoming states, read the transcript of the Washington Post’s live chat with Larry Sabato, the founder of the Center for Politics at the University of Virginia. Also, read the latest coverage in the Washington Post and Baltimore Sun.

Obama is way ahead of Clinton, 52 percent to 32 percent, in Maryland, according to a SurveyUSA poll conducted Feb. 7-8. Margin of error is 3.7 percent. The two run roughly even among white voters, but Obama leads 71 percent to 18 percent among black voters and Clinton’s margin among Hispanics is smaller than in many other places, 48 percent to 42 percent. (See a Chicago Tribune story about the reasons behind Clinton’s strength with Hispanics). Obama leads Clinton on almost ever major issue except Social Security. A Rasmussen Reports poll taken Feb. 6 shows Obama with an even wider 57 percent to 31 percent lead, with a 4 point margin of error. Rasmussen also says white voters split about even while Obama leads 82 percent to 12 percent among black voters.

SurveyUSA says Obama also has a big lead in Virgina, 59 percent to 39 percent, with a 4.1 percent margin of error. As in Maryland, they run neck-and-neck among white voters while Obama has a 7-to-1 lead among black voters. These results are mirrored again by a Rasmussen Reports poll that has Obama winning 55 percent to 37 percent, and showing similar numbers to SurveyUSA on how they are doing among white and black voters. The margin of error is 4 percent. The poll was conducted Feb. 6-7.