A DECADE ago Newt Gingrich’s Republican revolutionaries seized control of Congress after 40 years of Democrat rule by promising to end the culture of graft and corruption on Capitol Hill.

Today, after a string of indictments, scandals and a criminal investigation that threatens to implicate dozens of politicians next year, the tables have turned full circle. It is now President Bush’s Republicans who are seen as the party of sleaze.

Polls suggest that two thirds of Americans believe that corruption is a serious political problem. That, allied with the growing unpopularity of the war in Iraq, is raising fears in the White House of a voter backlash in next year’s mid-term congressional elections.

Since the summer, leading Republicans have been hit by a steady stream of scandals.

In September Tom DeLay, one of the most powerful politicians in America, had to step down as leader of the House of Representatives after being indicted for violating election finance laws. He is vigorously contesting the charges.

Bill Frist, the Republican leader of the Senate, is also under investigation over insider trading allegations involving the sale of his stock in a healthcare company. Mr Frist has denied any wrongdoing.

How the Bush Administration led the country into the Iraq war, and Democrat accusations that the White House manipulated prewar intelligence, then dominated much of October and November after the indictment of Lewis “Scooter” Libby, the former chief of staff to Dick Cheney, the Vice-President, for his role in the Valerie Plame CIA-leak affair. Mr Libby was charged with perjury and obstruction of justice, and he too has pleaded not guilty.

This week Patrick Fitzgerald, the special prosecutor leading the CIA-leak investigation, convened a new grand jury to investigate further the role of Karl Rove, Mr Bush’s chief political adviser, in the Plame affair. The move suggests that Mr Fitzgerald may yet bring charges against Mr Rove.

Meanwhile, Randy “Duke” Cunningham resigned from the House of Representatives two weeks ago in one of the most spectacular cases of political corruption in recent years.

Mr Cunningham, a Republican congressman since 1991 and member of the House Defence Appropriations committee, admitted accepting $2.4 million (£1.4 million) in bribes from defence contractors, including a Rolls-Royce and a $7,200 antique Louis-Philippe commode.

But of greatest concern to White House strategists is a criminal investigation by the Department of Justice into a Republican lobbyist named Jack Abramoff that could lead to the indictment of several politicians — mostly Republican — next year.

Over the past two years other investigations have exposed an intricate web of contacts between Mr Abramoff, one of the most powerful Republican lobbyists in Washington, and senior politicians.

Mr Abramoff allegedly gave them millions of dollars in donations as well as gifts, meals at top restaurants and lavish overseas trips, including golfing holidays at St Andrews. In return he sought legislative favours on behalf of his clients.

Last week Michael Scanlon, an Abramoff business partner and former aide to Mr DeLay, pleaded guilty to conspiring to bribe public officials and defraud several Native American tribes. The tribes had hired Mr Abramoff to lobby politicians to get legislation favouring their gambling interests.

Scanlon is thought to have agreed to provide prosecutors with evidence that politicians took money in direct exchange for favourable votes.

One of the congressmen Scanlon is accused of bribing has been identified as Bob Ney, a Republican from Ohio. Mr Ney has been subpoenaed by a grand jury investigating Mr Abramoff, and denies wrongdoing.

It is alleged that, in addition to $14,000 in campaign contributions, Mr Ney received from Mr Abramoff’s Native American clients, he also got a golfing trip to St Andrews.

Among others who went on a St Andrews trip was Mr DeLay, who once described Mr Abramoff as my “dear friend”. The cost of Mr DeLay’s trip went on the lobbyist’s credit card.

Another Abramoff friend and former associate who went to St Andrews was David Safavian. He was forced to resign as the White House’s chief procurement officer in September after being charged with obstructing the Government’s investigation into his dealings with Mr Abramoff.

More than 30 members of Congress have been revealed to have taken legislative action favourable to Mr Abramoff’s Native American gambling clients after receiving money from the lobbyist or the tribes. Most are Republican, but they include Harry Reid, the Democrats’ Senate leader, and another Democrat senator, Byron Dorgan, of North Dakota.

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