Raleigh, N.C. — For the third time in a week, a poll of North Carolina voters shows the race between Democratic presidential candidates Barack Obama and Hillary Clinton to be tightening up.

Rasmussen Reports surveyed 831 likely Democratic voters statewide on Thursday and found Obama's lead in the state is down to single digits. The poll has a margin of error of 4 percentage points.

Obama leads Clinton 49 to 40 percent in North Carolina, according to the poll. A Rasmussen Reports poll conducted Monday showed Obama with a 51 to 37 percent lead, down from a 23-point lead in early April.

A poll conducted by Mason-Dixon Polling & Research Inc. early this week showed Obama with a seven-point lead.

Controversial comments by Obama's former pastor, the Rev. Jeremiah Wright, appear to be dragging the candidate down, according to the latest poll.

Eighty percent of those surveyed said they had followed new stories of Wright, who has been criticized for statements against President George W. Bush and the Iraq War and for accusing the U.S. government of creating the AIDS virus to destroy minorities.

Two of every five voters said they believed Obama denounced Wright's comments for political purposes, while another 43 percent said they believed the candidate was outraged by the comments, according to the poll. Forty percent of respondents said it was at least somewhat likely Obama shared some of Wright's views.

Obama is still viewed favorable by 69 percent of those polled, although that is down six points from early April. Clinton is viewed favorably by 61 percent, down five points from last month.