"It's going to be a difficult cycle for Democrats," said Stuart Rothenberg, publisher of the non-partisan Rothenberg Political Report.

Gordon is one of 11 Democrats who have announced they will not run for re-election. On the Republican side, 12 House members are retiring or running for another office, such as Delaware's Mike Castle, who has announced his bid for the Senate seat long held by Vice President Biden. Rothenberg rates seven of the Democratic open seats as potentially changing parties, compared with three Republican open seats.

"We have more swing districts overall," said Rep. Chris Van Hollen, a Maryland Democrat who heads his party's congressional campaign committee. "We've said from Day One that this is going to be a very challenging cycle."

Both parties work hard to keep retirements to a minimum, because incumbents generally have an advantage in winning elections. In 1994, the retirement of 28 Democrats proved the harbinger of a Republican takeover of the House.

Democrats who have announced retirement plans so far have all done so for personal reasons, Van Hollen said, but he acknowledged he's talking to others who are worried about next year's election. "We are … assuring them they are going to have strong support," he said.

Campaign finance reports filed last month with the Federal Election Commission showed Van Hollen's Democratic Congressional Campaign Committee with $14.5 million in the bank. The National Republican Congressional Committee had $4.2 million.

Gordon is the third member of the Blue Dog Coalition, a group of centrist Democrats, to announce plans to retire since Nov. 23. The others are Reps. John Tanner of Tennessee and Dennis Moore of Kansas. Another deficit hawk, Rep. Brian Baird of Washington, announced his retirement last week.

Rep. Jim Matheson of Utah, a co-chair of the Blue Dog Coalition, said Democrats need centrists to maintain their 81-seat edge in the House.

"Blue Dogs have a proven track record of winning in moderate-to-conservative districts," he said. "The next election cycle will be no different."

Republicans say it's no accident that moderate Democrats are opting not to face the voters next year. "Blue Dog Democrats would rather roll over and retire than face the political headwind that is barreling toward them," said Ken Spain, a spokesman for the Republican congressional committee.

Former congressman Charles Stenholm, a Texas Democrat who helped found the Blue Dog Coalition, said he thinks that some of his former colleagues are feeling frustrated and under siege.

"It's better to go out on your own terms than to be forced out," said Stenholm, who served 26 years in the House before losing his seat in 2004.

By Kathy Kiely, USA TODAY