Mr DeLay's departure deprives the party of arguably its most powerful figure on Capitol Hill, an unmatched political organiser and enforcer who has done more than anyone to drive President George Bush's agenda through a bitterly divided and partisan Congress.
But not only on Capitol Hill has he ruled the Republican flock with a rod of iron. The 58-year old Texas congressman has also been a prime architect of his party's so-called "K Street Project", using a combination of carrots and sticks to place Republicans at the head of the lobbying firms and business interest groups which play a central role in shaping legislation here.
Even Democratic opponents who detest him grudgingly admit there has been no more effective majority leader from either party in the past 20 years.
But for Republicans the affair of Mr Delay - charged with criminal conspiracy over alleged illegal campaign fundraising for the 2002 elections to the Texas state legislature - is only the latest in a series of ethics controversies involving major party figures, stretching from Capitol Hill and the lobbying industry into the White House itself.
Known as the Hammer for his ruthless style, Mr DeLay helped to create the current Republican golden age in Washington. He was a close lieutenant of the former speaker Newt Gingrich, who led the party to victory in the 1994 mid-term elections, by seizing on public discontent with an entrenched, corrupt and complacent Democratic majority. The wheel may now be turning full circle. The host of scandals now threatens to tar the Republicans in exactly the same fashion.
Just like Republicans 11 years ago, Democrats scent blood. The DeLay affair, said the House minority leader Nancy Pelosi, is "the latest example that Republicans in Congress are plagued by a culture of corruption."
The pile of supporting evidence for that claim is growing almost by the day.
From a Republican perspective, the best hope is that Mr DeLay himself will be sidelined for only a few weeks. At worst, however, he could find himself being handcuffed and photographed as an alleged felon.
Meanwhile Bill Frist, his counterpart in the Senate, is under separate federal investigation for suspected insider trading, in connection with the sale of shares in his family hospital company shortly before the stock price fell sharply. Like Mr DeLay, Mr Frist denies any wrongdoing, but the very fact of an investigation is embarrassment enough.
Related trouble is brewing on the lobbying front. Jack Abramoff, a disgraced Republican lobbyist who once had close ties to Mr DeLay, has been charged with fraud, and may be tempted to incriminate leading party figures as part of a plea bargain with FBI investigators.
The same goes for David Safavian, a former White House budget aide who resigned earlier this month,days before he was indicted for perjury and obstructing the Abramoff inquiry.
That case has only escaped wider coverage because it has been overshadowed by greater disasters for Mr Bush in the most troubled spell of his presidency. They include the seemingly intractable insurgency in Iraq, his inept response to Hurricane Katrina, and public disgruntlement at soaring petrol and fuel prices, always an especially sensitive issue for a US leader.
Meanwhile the White House is bracing for the conclusion of the investigation by an independent prosecutor into the leak of the name of the CIA operative Valerie Plame, which has already seen Karl Rove and other senior administration officials testifying before a federal grand jury.
Congressional Republican leaders have replaced Mr DeLay with the Missouri congressman Roy Blunt on a "temporary" basis - on the assumption that the Texan's protestations of innocence are true and that he will be speedily exonerated.
But Mr Blunt is under a small ethics shadow of his own. According to the Associated Press, records on file with the Federal Election Commission show that Mr Blunt's political action committee has paid some $88,000 (£50,000) in fees since 2003 to a consultant facing indictment in Texas in the DeLay case.Reuse content