Rep. Tom DeLay leaves a troubling legacy for Republicans as they face re-election.

The Texan, once one of the most powerful and feared leaders of Congress, joined Newt Gingrich in helping to lead Republicans to power in 1994. But he later became a symbol of the widening ethics scandal that now clouds the party’s prospects for continued control.

Republicans face voters weary of corruption allegations and the heavy-handed tactics DeLay came to personify. At the same time, Republican candidates are further weighed down by President George W. Bush’s low approval ratings and the unpopularity of the war in Iraq.

“It’s hard to believe that in just 12 years, Republicans could end up in the same situation that it took Democrats 40 years to get in,” Republican strategist Frank Luntz said.

Luntz, who was once Gingrich’s pollster and helped orchestrate the 1994 “Contract With America”, a set of unifying Republican policy initiatives, said the party’s current majority now seems “tired”, and those speaking out for change and innovation “are just not being noticed”.

Republicans hold 231 of the 435 seats in the House of Representatives. Democrats have 201. There is one independent and two vacancies.

DeLay said on Tuesday he would resign from Congress rather than seek a 12th term so as not to hurt Republican chances. He acknowledged his re-election prospects were threatened by scandal.

The voters of his Houston-area district “deserve a campaign about the vital national issues that they care most about and that affect their lives every day and not a campaign focused solely as a referendum on me,” DeLay said.

He had resigned as House majority leader last fall after a grand jury in Texas indicted him, accusing him of funnelling illegal corporate contributions into state legislative races. In January, he decided against trying to get the leadership post back amid a spreading election-year corruption scandal.

Former lobbyist Jack Abramoff, once a close DeLay ally, and two of DeLay’s former aides have pleaded guilty in a Justice Department corruption probe and are cooperating with prosecutors.

DeLay denied anew on Tuesday that he had done anything wrong. “I’m not stupid,” he said in an interview on MSNBC television.” He said he had checked with lawyers to make sure every one of his actions was within the law and House rules.

“My lawyers have been told I’m not a target of the investigation,” DeLay said. He said he managed his congressional office “by trusting the people I hired. Evidently, they mishandled that trust.”

The Texas congressman said hoped to travel the United States to help unify the conservative movement and hoped to remain influential in Republican politics. He suggested he could do that better outside the Congress.

“It’s quite evident to me in the last couple of months that being a rank-and-file member, I’m not able to accomplish the things I have been able to accomplish,” he said.

DeLay’s resignation “marks the end of a 12-year reign of unquestioned Republican dominance and casts a shadow on the chances of Republicans in the fall elections,” said Ross Baker, a political scientist at Rutgers University who specialises in Congress.

Under DeLay’s sometimes iron-fisted rule, House Republicans marched pretty much in lockstep during Bush’s first term, delivering one legislative victory after another. “Republicans, however loyal they may have been in the past, are now taking an every-man-for-himself attitude,” Baker said.

Congress draws even lower public opinion ratings than the president. An AP-Ipsos poll last month showed only 31 percent of those surveyed approved of the job Congress was doing, compared with 37 percent for Bush.

When people were asked if they wanted to see Republicans or Democrats win control of Congress, Democrats got more backing, by 47 percent to 36 percent.

Democrats have used DeLay’s legal problems and those facing other Republicans — among them Senate Majority Leader Bill Frist and former vice presidential chief of staff I. Lewis (Scooter) Libby — to claim that Republicans are in the grips of a “culture of corruption”, an assertion they repeated on Tuesday.