The one-count indictment accuses DeLay of conspiring with two associates, John Colyandro and James Ellis, to illegally funnel corporate contributions to candidates for the Texas Legislature.
House Speaker Dennis Hastert of Illinois moved quickly yesterday to tap an interim replacement for DeLay, elevating Rep. Roy Blunt of Missouri, a DeLay protege and his successor as the No. 3 whip.
The move was designed to bring some stability to an unsettled and increasingly fractious Republican Conference as lawmakers eye the possibility of a future without one of their most powerful and effective - albeit controversial - members.
Leaders said the change in leadership would not torpedo their ambitions for the rest of the year.
"The conference has to go on," Hastert said. "We have work to do."
Showing flashes of the hot temper that earned him the nickname "The Hammer" during his years as chief nose-counter in the House, DeLay branded Texas District Attorney Ronnie Earle - the Democrat who brought the indictment - "an unabashed partisan zealot" who had abused his power.
"I am innocent," DeLay, 58, an 11-term House veteran, told reporters in a brief mid-afternoon appearance in his Capitol office. "Mr. Earle and his staff know it, and I will prove it."
DeLay called the indictment weak, and said it was political retribution for his prominent role in pushing through a hard-fought Texas redistricting plan that cost Democrats House seats.
"I have the facts, the law and the truth on my side," DeLay said.
The White House offered a tepid expression of support for DeLay, as aides said President Bush would withhold judgment about the indictment until the Texas case unfolded.
DeLay "is a good ally, a leader who we have worked closely with to get things done for the American people," said Scott McClellan, the White House spokesman.
For now, the indictment has darkened the ethics cloud over DeLay, already stung by allegations that he took luxurious foreign trips paid for by embattled lobbyist Jack Abramoff, a close friend, in violation of House rules.
Democrats signaled they would use DeLay's indictment as evidence of a pattern of unscrupulous Republican behavior.
Howard Dean, the party leader, said the grand jury had done "what the Republican-controlled federal government has failed repeatedly to do, which is hold Republicans in Washington accountable for their culture of corruption."
DeLay's indictment carries with it a sentence of six months to two years in a state prison and a fine of up to $10,000. House Republican rules mandate than any member indicted on charges carrying a sentence of two years or more give up his or her leadership post. In a show of solidarity with DeLay last year, Republicans scrapped the rule; but they reversed themselves in January, chastened by a backlash in their ranks.
The charges announced yesterday allege that DeLay conspired to use a political action committee he created, Texans for a Republican Majority, to divert corporate campaign contributions to seven Texas candidates. Texas law bars such corporate contributions. The indictment accuses DeLay of participating in a scheme in which corporate donations were sent to the Republican National Committee and exchanged for funds raised from individuals - which are allowed under Texas law - before being passed on to the candidates.
Colyandro and Ellis, who were indicted for money laundering in the case, handled the transaction, according to the charges. Another DeLay associate, Warren RoBold of Maryland, was also charged in the 2004 indictment. Yesterday's indictment doesn't specify what role DeLay is alleged to have played.