Maybe it’s the crummy national environment or maybe it was the topless attack ad, but a new Democratic poll in California’s 3rd district shows that Rep. Dan Lungren (R) may not be safe.

An Oct. 4-6 survey by Fairbank, Maslin, Maullin and Associates (D) for physician Bill Durston (D) showed Lungren leading his Democratic challenger 33 percent to 30 percent. A large 30 percent of the electorate was undecided, according to the poll.

Two years ago, Lungren defeated Durston 60 percent to 38 percent, with two third-party candidates combining for less than 3 percent of the vote.

This cycle, Durston has been attacking the Congressman for taking junkets and money from special interests, culminating with a television ad of a shirtless Lungren walking poolside in swim trunks. Democrats have also narrowed their voter registration deficit in the district from 6 points to 4 points.

Of course, a majority of the undecided voters may end up breaking Lungren’s way in a district where President Bush garnered 58 percent of the vote in 2004. But Republican candidates can’t afford to take those voters for granted this cycle.

“Dan Lungren has done a great job representing the constituents in his district, and we’re confident the seat stays in Republican hands,” said Karen Hanretty, the National Republican Congressional Committee communications director.