President Bush has lost one of his most important political allies in Congress, at least temporarily. The criminal indictment of Texas Congressman Tom DeLay, the Republican majority leader in the House of Representatives, is likely to complicate the efforts of the president and congressional Republicans to regain their political footing, in the wake of public concern over Iraq and the government's response to Hurricane Katrina.

Congressman DeLay has had a crucial role in pushing the Republican agenda in Congress ever since his party retook control of both the House and Senate in 1994.

With his indictment by a Texas grand jury on alleged campaign finance violations, Congressman DeLay must temporarily give up his party leadership post, even though he retains his seat in Congress.

"As for the charges, I have the facts, the law and the truth on my side, just as I have against every false allegation my opponents have flung at me over the last 10 years," said Mr. DeLay.

Congressman DeLay says he is the victim of a political vendetta by Texas prosecutor Ronnie Earle, a Democrat.

Mr. Earle says he has prosecuted Democrats as well as Republicans over the years, and is merely trying to enforce Texas law.

"Corporate contributions to political campaigns are illegal in Texas, and the law makes such contributions a felony. My job is to prosecute felonies," said Mr. Earle. "I am doing my job."

The DeLay indictment is the latest in a series of setbacks for Republicans. The Republican leader in the Senate, Bill Frist of Tennessee, is facing a federal probe of a stock sale, in which he says he did nothing wrong.

Opposition Democrats contend that Tom DeLay's legal troubles represent the arrogance of Republican power, even though some Democratic lawmakers have also had ethics problems in recent years.

"Yesterday's [Wednesday] criminal indictment of Majority Leader DeLay is the latest example of Republicans in Congress being plagued by this culture of corruption," said California Congresswoman Nancy Pelosi, the House Democratic leader.

Tom DeLay is nicknamed the 'Hammer' for his blunt style of political arm-twisting. He has been very effective in rounding up support for the president's agenda in Congress, and some Republicans worry that his departure could hurt the prospects for future action on the administration's priorities.

Presidential spokesman Scott McClellan says Mr. Bush is determined to push ahead.

"The Republican Party, particularly under this president, has worked to get things done for the American people," he said. "We have advanced an agenda that has helped to improve the quality of life for all Americans."

Political analysts say the DeLay indictment could pose some problems for Republicans, as they prepare to defend their Senate and House majorities in next year's congressional elections.

"No member of Congress wants to have his name in the same sentence with the word, indicted," said Stuart Rothenberg, who publishes an influential political newsletter in Washington. "When you have a leader, a high profile leader, with legal problems, you have not only a leader with a headache, but a party with a headache."

Recent public opinion polls show declining support for the president because of the situation in Iraq and the much criticized federal response to Hurricane Katrina.

University of Maryland political expert William Galston says Mr. Bush, whose second and final term ends in 2008, will have to push his agenda in Congress hard over the next year, in order to maximize his remaining political clout.

"After the November 2006 congressional elections, all political energy will turn towards [2008] presidential contests, which will be wide open in both parties," said Mr. Galston. "What the president does not accomplish between now and the end of next summer, he will not accomplish. So, the window, which was always narrow, is now closing more rapidly than he would like."

Tom DeLay is the latest in a series of high-profile congressional leaders from both parties to face legal or ethical problems.

Former Republican House Speaker Newt Gingrich was reprimanded by the full House in 1997, and fined $300,000 for ethics violations.

In 1989, Democratic House Speaker Jim Wright was forced to resign after the House Ethics Committee found that he had violated dozens of congressional rules.