Sen. Arlen Specter's lead over Rep. Joe Sestak in the Democratic Senate primary has dwindled to 9 percentage points, according to a just-completed poll conducted for another campaign.

Specter led 47 percent to 38 percent in the survey of 600 likely primary voters interviewed by telephone on Tuesday and Wednesday of this week. A little over a month ago, a poll for the same campaign found Specter with a 23-point advantage, leading Sestak, 52 percent to 29 percent.

Interestingly, almost all of Specter's advantage in the more recent poll comes from African Americans. The poll found the race essentially tied among white Democrats, (44 to 42 percent, Specter) but Specter had a 4 to 1 lead among blacks - 67 percent to 16 percent.

That makes good African American turnout, particularly in Philadelphia, a key part of any Specter victory scenario.

Today, Specter's campaign began airing an advertisement featuring President Obama on black radio stations in the city. And Sestak went to West Philadelphia to discuss policies to encourage job development.