Republican Dean Scontras is gaining ground on Rep. Chellie Pingree, but the Democratic incumbent still holds a 15-point lead in their race for one of Maine’s two seats in the U.S. House of Representatives.

The third Maine Poll sampled 305 registered voters in Maine’s 1st Congressional District on Sunday and Monday. Forty-eight percent said they would vote to keep Pingree in office while 33 percent said they preferred Scontras, a businessman from Eliot who is running in his first general election.

The bloc of undecided voters — 18 percent — remained virtually unchanged from two earlier versions of the Maine Poll.

The earlier polls, taken in September and early October, showed Pingree with leads of 24 and 28 percentage points, respectively.

“There’s movement,” Scontras said Wednesday during a break from campaigning in Rockland. “I’m glad to see it’s moving in the right direction. I think this will continue to tighten.”

The poll showed Pingree maintaining a considerable advantage among women (52 percent to 27 percent) and voters who identify themselves as unenrolled or independent (53 percent to 24 percent).

She also fared well among voters with college degrees (55 percent to 31 percent) and those reporting household incomes between $50,000 and $100,000 (56 percent to 26 percent).

“It’s not surprising that polls are all over the place, to a certain extent, because this is a very volatile year,” said Pingree’s spokesman Willy Ritch. “But as the voters learn about Dean Scontras’ risky positions, I think they’re going to decide that he’s not right for Maine.

“He doesn’t think that we should increase the minimum wage and he’s promised to protect tax breaks for companies that send jobs overseas. And that’s not good for Maine families,” Ritch said.

The party breakdown among voters who were surveyed was 36 percent Democratic, 32 percent Republican and 25 percent independent or unenrolled. The breakdown of voters who turned out for the 2008 election was 34 percent Democratic, 27 percent Republican and 36 percent unenrolled.

Voters identifying their political leanings as conservative favored Scontras 61 percent to 22 percent. Those who described themselves as liberal went for Pingree, 81 percent to 9 percent. She also pulled in more than twice as many moderates, 52 percent to 23 percent.

Scontras said he got a standing ovation at the Rockland Rotary Club on Wednesday.

“The reception has been fantastic, and I’m in Knox County, her backyard,” he said, referring to Pingree’s North Haven home. “I’ve been out talking about the fact that she voted for health care, cap and trade, and card check, and has increased the federal debt considerably. Everywhere I go, that message is warmly received.”

Scontras appeared Monday on CNBC, a national cable business news station, and drew further attention Wednesday when the Boston Herald reported that Rep. Barney Frank, chairman of the House Financial Services Committee, flew to the Virgin Islands last year on the jet owned by Pingree’s fiance, hedge fund manager S. Donald Sussman.

“The whole Barney Frank portion of this episode has brought new life to that issue, so we’re getting a lot of calls about that,” Scontras said.

Scontras said he has held more than 50 town hall-style meetings in Maine and appeared at numerous breakfast and business club gatherings.

“And everything I hear,” he said, “is about the contrast between my message, which is less government, and her message, which is more government.”

Staff Writer Glenn Jordan can be contacted at 791-6425 or at: gjordan@pressherald.com