With crucial mid-term elections barely a year away, control of the House of Representatives, of which DeLay was majority leader until the indictment required him to stand aside, could come down simply to whom the voters believe.

'The Republicans' biggest fear is not the trouble that DeLay is in, but that people will come to see this Congress as corrupt,' said David Lanoue, chairman of political science at the University of Alabama.

'They know the story because the same thing happened to the Democrats in 1994. Each little scandal was just another paper cut, but ultimately they bled to death.'

DeLay, 58, one of the most abrasive, controlling and feared politicians in the Bush administration, insists the conspiracy and money-laundering charges laid against him by two Texas grand juries are nothing but a political witch-hunt.

'This is one of the weakest, most baseless indictments in American history,' he said. 'It's a sham.'

But Ronnie Earle, the district attorney for Travis county, Texas, stands by the outcome of a three-year investigation by the county's Public Integrity Unit that he says proves DeLay was behind a complicated and illegal scheme to redirect US$190,000 in political donations to support Republican candidates at state level in the 2002 elections.

'Texas law makes it a felony for corporations and labour unions to contribute money to political campaigns,' Mr Earle told Time magazine. 'My job is to prosecute felonies. I'm doing my job.'

DeLay has dismissed Mr Earle, a Democrat, as 'a rogue prosecutor' and 'an unabashed partisan zealot' out for personal gain. But the 63-year-old Mr Earle says that of the 15 public officials he has prosecuted in almost three decades in office, 12 were Democrats. The DeLay investigation 'is the most important of my career', says the man who abandoned his own retirement plans to see it to a conclusion.

The scandal has also revived allegations of gerrymandering. The 2002 election gave the Republicans a majority in the Texas legislature, which then embarked on a highly controversial plan pushed through by DeLay that redrew electoral boundaries. As a result, the state sent 21 Republicans to Congress last year, six more than previously, boosting the party's majority in the House and strengthening DeLay's own political power base.

The career of Thomas Dale DeLay has been dogged by controversy ever since he turned his back on the pest-control business that had made him rich and decided to run for election to the Texas House of Representatives in 1978.

As a student, he was expelled from Baylor University, Texas, for drinking, and battled alcoholism through much of his early career. His father Charlie, an oil worker who took his family to Venezuela for five years when his son was nine, and his two brothers, Ray and Randy, were also alcoholics.

After his election, he continued to drink heavily and endorsed the social lifestyle of a young and ambitious politician about town. During that time, DeLay was by his own admission downing 'eight, 10, 12 martinis a night at receptions and fund-raisers' and lived up to his 'Hot Tub Tom' image to the full. There was no shortage of all-night parties, booze and girls.

DeLay says his salvation came soon after he was elected to the US House of Representatives in 1984. During his first year in Washington, fellow congressman Frank Wolf of Virginia befriended him and introduced him to a video by a respected child psychologist and Christian preacher about the damage inflicted on families by fathers who were too busy to love their children.

'It told me what a jerk I really was,' DeLay admitted to The Washington Post. 'I was totally self-centred. It was me, me, me, me, me. It was golf or my business or politics that came first.'

DeLay, who married his high-school sweetheart, Christine Furrh, in 1967 and had a daughter, Danielle, in 1972, said the video made him reassess his life's priorities.

'I started crying because I had missed my daughter's whole childhood. My daughter asked her mother if 'somebody had adopted Daddy' because 'he was never around',' he said.

Soon afterwards, DeLay gave up drinking and turned to Christianity, and in the years since has wholeheartedly embraced a family-first, conservative anti-abortion and pro-gun-freedom agenda that has won substantial support, both political and financial, from those on the religious right.

He came to prominence as a vocal junior congressman and outspoken critic of the Democratic majority in the House during the 1980s and became deputy to then-minority whip Dick Cheney, now the vice-president, in 1988.

When the Republicans assumed control of the House in 1994, DeLay was elected majority whip and slipped easily into his new role as an enforcer, maintaining party discipline, ensuring the presence of enough representatives to swing close House votes and cracking down on anyone who stepped out of line.

Privately, he is known to relish his new nickname as The Hammer, also the title of an unofficial and critical 2004 biography, and his reputation as 'the meanest man in Congress'.

He is said to keep two leather bullwhips on display in his office alongside a stone replica of the Ten Commandments, and will happily point out to anyone that a hammer is a key tool of a skilled craftsman.

His financial clout also stands him in good stead in Republican circles. He oversaw the collection of almost US$30 million in campaign funds in 1999 - brazenly telling big corporate donors that 'if you want to play in our revolution, you have to live by our rules' - and brought in almost twice as much as House Speaker Dennis Hastert before the 2004 presidential election.

But the House Ethics Committee has admonished DeLay on three occasions, including one episode in which he is said to have offered to endorse one politician's son for elected office in exchange for his vote on a crucial health-care bill.

In 2002, with his elevation to the role of majority House leader, DeLay had achieved his ambition of becoming one of the most powerful Republicans in Washington. It also made him a target.

'There's no doubt that Tom DeLay is a lightning rod,' said Professor Lanoue. 'And even more so now. The best thing that could happen for him and the Republicans is for the charges to be dropped quickly, because the longer it goes on, the less likely it is that he can return to his job.' He believes DeLay's best defence tactic will be maintaining forcefully that the charges are politically driven, but he would need to take care.

'He's fighting in two arenas,' he said. 'He's fighting in the arena of public opinion, where he has to salvage his reputation if he wants to be a player in American politics again. But he's also fighting in the judicial arena and has to take the advice of his lawyers.

'I don't expect to see him cut an abrasive figure in court. That sort of thing doesn't play very well with juries.'

Adding spice to the forthcoming legal battle, which carries the possibility of a life sentence for the money-laundering charge, is DeLay's choice of lawyer Dick DeGuerin to head his legal team. Mr DeGuerin handed Mr Earle one of the biggest defeats of his career in 1994 when Texas treasurer Kay Bailey Hutchison, now a US senator, was acquitted of using state employees and resources to help her election campaign.

Meanwhile, Republican leaders are trying to gauge the possible impact on the electorate of the DeLay scandal and a Securities and Exchange Commission inquiry into a suspicious stock deal by Bill Frist, the Senate majority leader.

'Neither one is good news for the party, especially because President Bush's magic appears to be gone,' Professor Lanoue said. 'It's certainly a confluence of very bad events. If people start thinking that all this smoke is evidence of one big fire, then the same thing that happened to the Democrats in 1994 could happen to the Republicans next year.

'The only good thing they can take from this is that it's happening now and not in eight months' time. There's still a year until the elections and a lot can happen before then.'