Democratic U.S. Representative Jim Moran, a 12-term Virginia liberal, on Wednesday became the third member of his party this week to announce he will not seek re-election in November.
The announcements came amid growing signs that President Barack Obama's party faces a steep climb in its bid to win control of the House of Representatives from Republicans in this year's elections.
Moran made no mention of the battle for the House in his announcement. He said he was ready to retire from Congress when his term ends this year.
"It's time to close this chapter of my life," Moran, 68, said in a statement.
Moran's district lies just south of Washington. He has represented Virginia in the House for more than 23 years and is a member of the chamber's powerful Appropriations Committee.
The announcement came just a day after New York Democrat Bill Owens of New York said he would not seek re-election this year after taking office in 2009. On Monday, Representative George Miller of California, an ally of House Democratic leader Nancy Pelosi, announced plans to leave at the end of his term this year.
On the Republican side, U.S. Representative Buck McKeon of California scheduled a statement for Thursday. His aides declined to elaborate to Reuters.
The Hill newspaper, which covers U.S. politics, legislation and members of Congress, cited sources close to McKeon saying he plans to retire at the end of this year. His departure could set up a competitive race in the southern California district he has represented since 1993.
David Wasserman, who tracks House races for the nonpartisan Cook Political Report, said the recent retirements show that "Democrats are not very optimistic about taking back the House."
Wasserman predicted that Republicans will not only retain the House, but increase their majority - which now stands at 233 to 200, with two vacancies - by up to 10 seats.
Wasserman said Republicans have an advantage in midterm elections because people who tend to vote in these non-presidential contests are generally older and more likely to vote Republican.
Democrats up for re-election also face voters who are increasingly critical of Obama, largely because of the botched rollout of the president's landmark healthcare program.
Despite the recent spurt in Democratic House retirements, 17 Republicans in the chamber have announced plans not to seek re-election this year, compared to 13 Democrats. The overall number of announced retirements reflects the historical average.
In his announcement, Moran praised the bipartisan $1.1 trillion spending bill, which is scheduled for a vote in the House on Wednesday. Moran has worked in a mostly gridlocked Congress in recent years.
"I've seen the appropriations process at its height, and more recently its nadir," Moran said.
"We've achieved a bipartisan agreement that deserves support. It represents a budgetary cease-fire and I hope a historic turning point in getting this necessary funding process back on track," the lawmaker said.
(Additional reporting by Richard Cowan; Editing by Amanda Kwan)