Public Policy Polling offers numbers indicating that in their home state of North Carolina, Republican senator Richard Burr is only up 5 points over Democrat Elaine Marshall. They have Burr at 38 percent, 33 percent for Marshall, and a surprising 10 percent for the Libertarian candidate, Michael Beitler.

In a post–Research 2000 world, I don’t want any quibbling with a pollster to be misconstrued. I think the PPP guys are good guys with generally solid methods. But for not-so-well-publicized reasons, Republicans tend to perform poorly when PPP surveys their own backyard.

Burr’s last total in SurveyUSA: 50 percent. His last total in Rasmussen: 44 percent. His totals in the three preceding polls by Rasmussen: 50, 50, 51. Burr’s total in the four preceding PPP polls: 46, 43, 43, 41.

Is it possible Richard Burr is at 38 percent? I suppose; it is possible that PPP is using some sort of better voter screen than everyone else, and/or it’s possible that Rasmussen’s likely-voter screen is weeding out too many Democrats. But when a pollster has been quoted as saying that he doesn’t want a particular candidate to win, it’s time to exercise some skepticism. This was an issue last year:

The problem, Republicans say, is that PPP is no impartial observer. The firm makes its money by serving as the pollster to an exclusively Democratic roster of clients, ranging from members of Congress to dozens of state legislative and city council candidates. And CEO Dean Debnam has given generously to North Carolina Democratic candidates — including in races where his firm has conducted independent polling. In the heat of last year’s competitive Senate race between former Sen. Elizabeth Dole (R-N.C.) and Democrat Kay Hagan, Debnam donated $5,400 to the Democratic Senatorial Campaign Committee. He also made two $2,300 contributions to Hagan’s campaign.

“We’re absolutely rooting in the race. We don’t want Richard Burr to get reelected. We wanted Obama to win last fall,” said [PPP's Tom] Jensen. “But our reputation is predicated on getting it right, and we’re not going to cook the numbers just to tweak Richard Burr’s nerves. They are what they are.” The firm’s unconventional method of serving partisan interests while conducting independent polls that are widely reported on by the media has raised hackles among Republicans like Burr, who are on the receiving end of bad numbers. At the national level, Republicans gripe that news outlets don’t always report on the firm’s Democratic background.

I like the guys at PPP, but at this point, you just can’t put too much faith in their North Carolina numbers, not until other pollsters start seeing similar numbers.

UPDATE: Also, note how their sample breaks down: 46 percent Democrat, 36 percent Republican, 18 percent independent. That’s a more heavily Democratic electorate than North Carolina had on Election Day 2008, when it split 42 percent Democrat, 31 percent Republican, 27 percent independent.