A poll on the open-seat Maine Senate race was released today showing Democrats could have trouble winning a three-way contest.

The Public Policy Polling survey showed Rep. Chellie Pingree, who’s considering running for the Democratic nomination, soundly beating GOP contenders. But when factoring in now-declared Independent candidate former Gov. Angus King, Pingree falls to second place behind King.

The poll was the source of  much discussion on Monday among Maine political operatives. Several unaligned Democrats privy to the results Monday were spooked and expressed uncertainty about a Democratic victory given the dynamics of a three-way contest.

“There’s certainly some concern that Angus would have broader statewide appeal,” one Maine Democratic consultant said.

There is also concern that Pingree and King would draw from the same well of voters if the Congresswoman were to run. Democratic Senatorial Campaign Committee Chairwoman Patty Murray (Wash.) did not rule out the possibility today that the DSCC could back King, according to a report in the Hill newspaper.

“I’m not going to get into the ‘what if’ games,” she told the newspaper.

PPP is a Democratic firm that conducts automated polls. The poll was administered to 1,256 Maine voters and had a margin of error of 2.8 points. At least one other robopoll was administered in the state mentioning Pingree over the weekend, but it was unclear which organization commissioned the poll.

Also weighing heavily on Democrats’ minds are the 2010 Maine gubernatorial results.

Republican Gov. Paul LePage, who had strong support from the tea party, eked out a win with 38 percent of the vote. Independent Eliot Cutler garnered 36 percent, with Democrat Elizabeth Mitchell getting only 19 percent.

Pingree issued a statement Monday evening, after King’s official announcement, that she is still deliberating over a Senate run. Former Gov. John Baldacci (D) is also considering running, but his numbers were not as strong as Pingree’s in the poll.

Roll Call Politics rates this race as Tossup.