Under pressure from the national Democratic organization that is responsible for getting U.S. House members elected, Rep. Mike Michaud of Maine announced Thursday night that he won’t run for the U.S. Senate seat being vacated by Republican Olympia Snowe.

The Democratic Congressional Campaign Committee feared that if Michaud ran for the Senate, it would harm the party’s chances of holding Maine’s 2nd Congressional District seat, which Michaud has held since 2002, according to Democratic insiders with direct knowledge of the situation.

“The DCCC folks and Democratic leaders in the House are pushing Mike to stay” in the House, one Democratic operative said earlier Thursday, speaking on condition of anonymity.

Michaud’s campaign wouldn’t comment Thursday night on his reasons for not seeking the Senate seat. Michaud said in a release that “I want to continue to represent the wonderful people of Maine’s Second District and keep working on the unique issues and challenges we face.”

After Snowe’s stunning announcement Tuesday that she will not seek a fourth term, Michaud took out nomination papers Wednesday morning to run for Snowe’s seat.

Democratic Rep. Chellie Pingree, who represents Maine’s 1st Congressional District, has said she is strongly leaning toward a run for Senate. She, too, took out nominating papers Wednesday.

Pingree’s district, largely covering southern Maine, is considered more Democratic than Michaud’s northern district — and much easier for Democrats to retain with another candidate if Pingree runs for the Senate.

“Of course the DCCC wants Michaud to stay, because they don’t want to have to defend a potentially competitive open seat,” said Nathan Gonzales, deputy editor of the nonpartisan Rothenberg Political Report, speaking Thursday before Michaud’s decision.

The Democratic Senatorial Campaign Committee, which works to get Democrats elected to the Senate, was doing polling this week to determine which Democrat might have the best chance of winning Maine’s Senate race, said state and national Democratic sources.

Regardless of that poll’s results, state and national Democratic operatives did not want to see Michaud and Pingree abandon their House seats for a primary battle in June. Their worst fear was that if both Democrats ran for the Senate, Republicans could win both of the House seats and retain Snowe’s seat.

“The bottom line is, depending on who lines up and gets nominated (from both parties), we could go 0 for 3 this year,” said a Maine Democrat who knows all of the candidates involved and has been involved in state and national politics for years, speaking Thursday before Michaud announced his decision. “We have to be very deliberate in picking the right candidates.”

Besides Michaud and Pingree, another high-profile Democrat took out nominating papers Wednesday for the Senate seat — former Gov. John Baldacci.

The Republican field for the Senate seat remained wide open Thursday as party leaders and likely GOP candidates considered their options.

The sole Republican in the race remained Scott D’Amboise, a tea party-affiliated candidate who was unknown before he entered the race last year.

On Thursday, independent Aaron Marston, a political newcomer, was the only person who took out papers for the Senate race.

Maine Republican Party Chairman Charlie Webster said Thursday that GOP leaders are discussing who would be the strongest Republican candidate in a three-way Senate race. He said they assume that former Gov. Angus King, an independent, will run in November.

King, who has said he is considering running, has until June to collect petition signatures. Candidates who want to run in the party primaries on June 12 have until March 15 to submit at least 2,000 voter signatures.

Webster said King — whom he described as a “liberal Democrat” — would take votes from the Democratic nominee, and that Republicans would stand the strongest chance in the general election with a candidate who believes in the core principles of the Republican Party.

“I think you will have a race with two Democrats and a Republican,” he said. “We need to be different than they are.”

While any candidate is free to run on their own, Webster said, Republican leaders have put together a short list of potential candidates and are trying to make a “careful” decision about which one would fare best in the general election.

Among the prominent Republicans considering the Senate race are state Senate President Kevin Raye and Richard Bennett, Maine’s Republican National Committee member. Bennett, a former Maine Senate president, lost the 2nd District congressional race to Baldacci in 1994.

Raye said Thursday that he understands he must decide quickly, but he is determined to make “as thoughtful a decision as possible.”

He said he is talking with Republicans who are interested in seeking the 2nd District congressional seat if he runs for Senate. Raye is already a declared candidate for the U.S. House seat.

State Sen. Debra Plowman, R-Hampden, has taken out nomination papers for the 2nd District race. Bangor Mayor Cary Weston is also considering a run for the GOP nomination, according to Republican sources.

It was unclear Thursday night how Michaud’s decision would affect their plans.

Three Democrats have taken out nomination papers for the 2nd District seat: House Minority Leader Emily Cain, former state Sen. Bruce Bryant and former Secretary of State Matthew Dunlap.

Bryant and Cain said Thursday night that they are out of race. Both said they took out nominating papers in anticipation of Michaud running for the Senate.

Anticipating that Pingree will run for Snowe’s seat, state Senate Minority Leader Barry Hobbins, D-Saco, took out nominating papers Thursday for her 1st District seat.

Hobbins, who is 60, first ran for Congress when he was 32. He said he will decide by Monday or Tuesday whether he will run for Pingree’s House seat.

Other Democrats who have taken out papers for the 1st District seat are state Sen. Cynthia Dill, Wellington Lyons, David Costa, state Rep. John Hinck and David Lemoine, a former state treasurer.

John Vedral, a Republican, took out papers Thursday to run in the 1st District.

Two other Republicans have taken out papers for the 1st District: state Senate Majority Leader Jon Courtney and Markham Gartley, a former secretary of state.

Snowe’s open Senate seat is attracting national interest.

The New York Post reported that Georgette Mosbacher, a businesswoman, GOP fundraiser and former wife of Robert Mosbacher, secretary of commerce under President George H.W. Bush, is thinking about buying a house in Maine and running for Senate as a Republican.

Meanwhile, Pingree made it clear in an email to supporters Thursday afternoon that she is strongly leaning toward running for the Senate.

Several national liberal groups already have called Pingree their preferred Democratic Senate candidate. The Washington-based Progressive Change Campaign Committee started a “draft Pingree” movement within an hour of Snowe’s announcement Tuesday.

The group said Thursday that nearly 7,000 people nationally had signed on to its online petition urging Pingree to run.

Pingree’s husband, S. Donald Sussman, is a financier, philanthropist and frequent Democratic donor who recently purchased a 5 percent equity stake in MaineToday Media through Maine Values LLC.

MaineToday Media owns and operates The Portland Press Herald/Maine Sunday Telegram, the Kennebec Journal in Augusta, the Morning Sentinel in Waterville and other media outlets in Maine.

MaineToday Media Washington Bureau Chief Jonathan Riskind can be contacted at 791-6280 or at:

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Staff Writer Tom Bell can be contacted at 791-6369 or at:

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