Updated

WASHINGTON -- The Blue Dogs may be losing their bark. Despite polls showing a desire for more compromise in Washington, the political climate for moderate to conservative Democrats in the House has continued to deteriorate.

The 2010 election dropped the number of so-called Blue Dogs from 54 to 25. And the shrinking continues.

Rep. Mike Ross of Arkansas will not seek re-election next year. Rep. Dan Boren of Oklahoma also plans to retire. Rep. Joe Donnelly of Indiana has opted to run for the Senate. Rep. Heath Shuler of North Carolina is reportedly being considered for the athletic director job at the University of Tennessee.

Other House members, such as Rep. Jim Matheson of Utah, face the prospect of running in less friendly congressional districts after their states complete redistricting. Rep. Jane Harman of California resigned earlier this year to run a think tank.

The early departures and the potential for more are feeding Republican hopes that they will win more of the country's swing districts in next year's elections and maintain their majority in the House. That also raises questions about whether the Blue Dogs as a group are in an extended decline as moderates from both parties disappear from Capitol Hill.

"The parties are becoming more polarized and that's unfortunate," Boren said. "The success of our political system weighs in the balance depending upon how many moderates, how many problem-solving pragmatists are going to be elected."

The Blue Dogs got their name by playing on an old Southern expression about the loyalties of Southern Democrats. The saying went that a Southerner would vote for a yellow dog if it were on the Democratic ballot, earning them the name Yellow Dog Democrats. A Blue Dog, the moderates reasoned, was a Yellow Dog "choked blue" by their more liberal Democratic colleagues.

Blue Dog lawmakers say that talk of their group's demise is overstated. When the balance of power shifts in Congress, they point out, it's generally those in the center who take the hardest hits.

"Basically, when the Republicans take over, they beat the conservative Democrats. When the Democrats take over, they pretty much defeat moderate Republicans," Ross said. "That's because when you're in a swing district, you're going to be a conservative Democrat or a moderate Republican, or you don't survive."

Lawmakers have several theories about why the ranks of moderates are on the decline.

Congressional districts are being drawn in a way that favors increasingly partisan representation from both parties. Also, much of the money flowing to campaigns these days comes from interest groups with a decidedly partisan edge, such as the Club for Growth on the right or labor unions on the left.

GOP leaders have their own interpretation as well for the Blue Dogs' decline. They say that party affiliation has drowned out the Blue Dogs' ability to demonstrate their independence.

"There's a group of Democrats that were recruited several years ago that came to Washington thinking that they could be welcome and fulfill a role within the Democratic Party," said Rep. Pete Sessions, R-Texas, the chairman of the National Republican Congressional Committee. "I think that over time these members have found out that they're in a pack of purebred liberals."

Ryan McConaghy, a director at Third Way, a centrist think tank, warned against drawing strong conclusions based on the 2010 elections and a few retirements. He said there will always be a role for the Blue Dogs coalition because a large segment of the Democratic base identifies itself as moderate.

"I think their numbers will ebb and flow," he said. "I don't see them growing extinct anytime soon."

The Blue Dog caucus was formed in 1995 after the GOP took control of the House for the first time in four decades. They focus on fiscal issues and describe themselves as centrists who believe it's necessary for both parties to compromise to tackle the nation's problems. In March, the group put forward a goal of trimming $4 trillion in national debt over the coming decade, with two-thirds coming from spending cuts and one-third from tax increases.

President Barack Obama subsequently pushed for a $4 trillion deal as well, but in the end, conservative Republicans wouldn't go along with any plan that resulted in higher taxes.

In the 2010 elections, the GOP tied the Blue Dogs to then-Speaker Nancy Pelosi as well as to the struggling economy. While members of the caucus voted against the party on individual pieces of legislation, it was rare for members to vote against all of the party's top priorities. For example, 34 Democrats voted against the health care overhaul, most of them Blue Dogs, but only six Democrats voted against the economic stimulus bill.

Even those who voted "no" on both measures, such as Reps. Gene Taylor of Mississippi and Walt Minnick of Idaho, found no escape from attack ads linking them to the Democratic priorities because they had voted for Pelosi as House speaker. "Put the brakes on Pelosi. Replace Walt Minnick," said one television ad.

In the end, many of the Blue Dogs were simply unable to distance themselves from the Democratic Party's leadership, despite voting against them on some key issues, said Burdett Loomis, a professor at the University of Kansas who has written extensively about the Blue Dogs.

"When push came to shove, they were Blue Dog Democrats, but they were Democrats," Loomis said.