A former House majority leader,Tom DeLay, argued yesterday that his resignation will boost the prospects of Republicans in this fall’s elections, but there was no sign that Democrats planned any letup in their drive to win back the House by painting the GOP as corrupt.

“I’m more interested in growing the Republican Party than my own future,” Mr. DeLay told Fox News. The Texas lawmaker said he decided not to seek a 12th term in Congress after concluding that he might lose to a Democratic challenger receiving support from liberal groups nationwide.

“It’s very nasty. Every leftist organization in America is down here in Houston,” said Mr. DeLay, who stepped down as majority leader in January as the scandal clouds gathered. “I just realized my constituents don’t deserve this.They deserve a Republican.”

Mr. DeLay’s abrupt decision came as he faced legal pressure on two fronts. He is expected to face a criminal trial in a Texas state court later this year on a charge that he unlawfully funded campaigns for the state legislature. Republican leaders have dismissed that case, brought by a Democratic prosecutor, as politically motivated.

The more ominous development for Mr. DeLay may have been the guilty plea in federal court on Friday of his former deputy chief of staff, Tony Rudy. Rudy admitted to joining with a since disgraced lobbyist, Jack Abramoff, in a conspiracy to corrupt members of Congress and defraud clients. In November, a former press secretary to DeLay, Michael Scanlon, also pleaded guilty to involvement in the scheme.

Rudy, Scanlon, and Abramoff are cooperating with prosecutors in a wide-ranging investigation of members of Congress, but Mr. DeLay said yesterday that his lawyers have been told he is not a target of the federal probe.”I have no fear whatsoever about any investigation into me or my personal or professional activities,” the former majority leader said in a videotaped message to his constituents.

Republicans in Washington seemed grateful for Mr. DeLay’s move to minimize his value as a target in this fall’s elections.

“My reaction was, it had to have been a very difficult decision for someone who loved representing his district in the state of Texas. I wished him all the very best,” President Bush said in response to a reporter’s question. “My own judgment is – is that our party will continue to succeed because we’re the party of ideas.”

The White House press secretary, Scott McClellan, pointedly declined to answer when asked if Mr. Bush tried to dissuade Mr. DeLay from exiting the political stage.

One Republican congressman, Christopher Shays of Connecticut, openly welcomed the former majority leader’s decision. “Tom DeLay stepping down is a good thing for Congress and my party,” Mr. Shays said. “It gives us a fresh chance to show the American people we are committed to changing business as usual in Washington.”

Democrats said Mr. DeLay’s departure would not alleviate their concerns about the tight bond that developed in recent years between lobbyists such as Abramoff and members of the Republican leadership.

“The issue about Congressman DeLay resigning is not about him,” Senate Minority Leader Reid said. “It’s about a culture of corruption that has developed in this Congress, the K Street project, airplane trips to play golf in Scotland, and all the other things we see with people pleading guilty who worked in his office.”

Democrats are hoping that voter dissatisfaction with Mr. Bush, the war in Iraq, and corruption scandals on Capitol Hill, will erase the Republicans’ narrow margin in the House and throw the body back into Democratic control.

A professor of politics at the University of Virginia, Larry Sabato, said Mr. DeLay’s move was wise, but may not be enough to keep Republicans in control of the House. “This removed him as headline fodder for the Democrats and the media all the way to November,” Mr. Sabato said.

The professor said he believed Mr. DeLay decided on his own to throw in the towel, probably after the guilty plea Friday from Rudy. With two former staffers admitting to felonies, the congressman was in an untenable position, according to political analysts.

“People are going to say either you knew, or you should have known,” Mr. Sabato said.”He looked at the numbers and said, ‘I’m going to lose.'”

Mr. DeLay told CNN yesterday he made the decision to resign before he knew of Rudy’s plea. He said he was disappointed in his former aides but had no knowledge of their lawbreaking. “I manage my office by trust,” he said in an interview on MSNBC’s “Hardball.” “Evidently, they mishandled that trust.”

Mr. DeLay said that scrutiny from left-wing groups led him to have lawyers vet all of his activities in recent years. “I would be absolutely the stupidest man in Washington to do anything illegal,” he said.

The round of interviews the former majority leader granted yesterday led to some surprising exchanges. Mr. DeLay, who often speaks of Democrats in scathing terms, was asked on MSNBC to name a Democrat with strong morals.

Mr. DeLay cited Rep. Barney Frank, who is openly gay. “He’s a strong, moral Democrat,” the former majority leader said. “I respect him greatly. He’s a true liberal and he’s unashamedly a liberal.”

Mr. DeLay said he does not agree with homosexuality, but said of Mr. Frank, “I’m not going to judge him.”