Rep. Chris Bell (D-Texas), a lame-duck lawmaker free from concern about political retribution, is carving out a legacy from his brief tenure in Congress: serving as House Democrats’ chief attack dog against Majority Leader Tom DeLay (R-Texas).

Bell on Tuesday formally filed a 187-page complaint with the Committee on Standards of Official Conduct against DeLay, calling his Texas colleague “the most corrupt politician in America today.” The filing marks the breach of a long-standing, though unwritten, truce between the parties on filing ethics complaints and the most aggressive stand by House Democrats who have for months charged the GOP with following a “pattern” of corruption.

Aides and Members insisted that Bell — who lost his Texas primary earlier this year following a DeLay-inspired round of redistricting — is acting on his own and not at the request of Democratic leaders as he seeks the inquiry into DeLay. And while House Democrats say Bell hasn’t sought to play the role of DeLay’s antagonist within the Caucus, if he is willing to take it on they privately welcome it.

“Bell believes DeLay is over the top and believes he’s in a unique position to do something without the ramifications of punishment,” said a senior Democratic staffer. “He probably views himself as someone who is able to do more than others can.”

“On this particular issue he finds himself in that role, whether he wants it or not,” added another Democratic leadership aide. “I don’t think he looks at himself as the Democrats’ attack dog, but that’s how he’ll be labeled by opposition and the role on this particular matter he will probably fulfill.”

Bell and his allies say the one-term Texas Democrat’s motivations are solid, adding that the charges against DeLay are substantive and serious and must be fully investigated. Bell said he has been looking into the allegations of wrongdoing for some time, and he brushed aside any suggestion that he is taking a new, more aggressive approach during his final months in Congress.

“I’ve never really viewed myself as a shrinking violet,” Bell said. “I’ve simply tried to provide good representation for the people back home.”

Another Democratic leadership aide said that, while no one asked Bell to take on the party’s tough battles, he is “a team player.” The aide said Bell truly believes DeLay engaged in illegal activity and is in a good position to take the lead because “he is leaving.”

Despite his ouster, Bell is widely viewed as having a political future beyond the 108th Congress, including a possible run for the Texas governor’s chair or the U.S. Senate. A well-liked Member, Bell was also seen as a rising star in the Democratic Caucus before his defeat at the hands of fellow Democrat Al Green.

Green and Bell squared off in the wake of an off-year round of Texas redistricting which DeLay pushed and Bell blames for his defeat.

In an interview with reporters Tuesday, DeLay said he had “the ultimate confidence in the ethics committee” to do “the right thing.” The Majority Leader said it is unfortunate Bell blames him for his primary loss, calling the Democrat “a disgruntled Member of the House.”

“Evidently [Bell] is very bitter about his loss in the primary, and he is using the ethics committee to express his frustration,” DeLay said.

Bell was adamant that the ethics complaint wasn’t political sour grapes or something intended to bolster either his or his party’s fortunes at the ballot box. Rather, he said, his goal is to find out the truth about DeLay and restore credibility to the House.

“The only thing I have to gain is the wrath of Tom DeLay,” Bell said. “I fully expect that. I fully expect retaliation.”

When asked whether he would encourage retribution by the GOP, DeLay said, “I do not encourage anyone to file complaints. If there are legitimate complaints” by Democrats or Republicans, “obviously I can’t discourage someone from doing something that is legitimate.”

Republican Members and aides said they planned to hold their fire until they see how the situation unfolds.

“I think if this thing were to escalate you would see us move on a number of [Democratic] leaders,” said a GOP lawmaker close to DeLay.

Beyond Tuesday’s complaint against DeLay, Bell recently took another aggressive stand during the Iraqi prison scandal. Bell was very vocal about his disgust over the incident and on Monday night lost an Armed Services Committee vote on forcing Defense Secretary Donald Rumsfeld to give Members all materials relating to Abu Ghraib.

Minority Whip Steny Hoyer (D-Md.) dismissed any labeling of Bell as an “attack dog,” but he did acknowledge the freshman lawmaker is “getting a lot of attention for raising these issues. There’s no doubt about that.”

Fellow Texas Democratic Rep. Martin Frost, who went toe-to-toe against DeLay on the state’s redistricting, said the issues raised in Bell’s complaint have been widely reported, and are worth investigating.

Asked about Bell taking the lead on the complaint, Frost said: “Chris Bell is an honorable person. He’s obviously someone who carefully considered this. I think he is obviously acting on his personal convictions.”

Rep. Ron Kind (D-Wis.) said he couldn’t speak to Bell’s motivations, but Democrats “have had concerns with some of the things DeLay has been doing for some time.”

Under the complaint filed Tuesday, Bell alleges DeLay engaged in a series of improper activities in recent years ranging from bribery, extortion, political money laundering and abuse of power.

Bell charged that DeLay sought and accepted political contributions for his Texas-based political action committee in return for legislative help; that he laundered corporate contributions to help Republicans in Texas legislative races; and that used his office to urge federal agencies to engage in a “partisan objective.”

Ben Pershing contributed to this report.