Symbolically as well as practically, the departure of Tom DeLay from Congress signals the end of an era of Republican dominance. The question now is whether the retreat that clearly has begun will turn into a rout.

The former House majority leader’s decision to abandon what increasingly appeared to be an uphill fight for re-election in his Texas district and retire from the House was the latest and by far the largest consequence of a widening inquiry of corruption on Capitol Hill.

It is one thing to see a Randy “Duke” Cunningham go to jail for bribery. Few outside his San Diego district had ever heard the name of the former Navy top gun before his spectacular downfall. Tom DeLay is a target of far larger size.

As prosecutors have extracted guilty pleas from lobbyists close to DeLay and former members of his staff, the ripples of scandal have threatened to spread through Republican ranks in the midterm election. Month after month, surveys are showing Democrats with a double-digit lead over the GOP in the voters’ preference for which party should control Congress.

Whether that translates to the specific victories needed to give Democrats an extra 15 seats and a narrow House majority cannot be guessed. But the relief his fellow Republicans expressed that they can now recruit a fresh and presumably unscarred candidate in the Republican-leaning DeLay district shows how nervous they are about holding on to the House.

It is almost as if they hope that by sacrificing their erstwhile commander, they can appease the public demand for change.

As much as Newt Gingrich embodied the aggressive strategy that enabled Republicans in 1994 to break the Democrats’ 40-year grip on the House, DeLay was the man who showed them how to consolidate – and use – their new power. As whip and then as majority leader, he built their fundraising and policy alliance with the business lobbies and social conservative movements, then used that leverage to impose party-line discipline on almost every key vote.

It was a commanding performance, and one that yielded a series of policy victories for President Bush. By putting the House Republican majority in lockstep with the White House, DeLay made it possible for Bush to prevail, not only over the outnumbered Democrats but also over the doubts harbored by some Senate Republicans about his agenda.

But DeLay also paid a price for his hardball tactics – and his tendency to push against the legal limits. He was admonished repeatedly by the House Ethics Committee. He faces prosecution in Texas over the financing of campaigns that delivered the Texas House of Representatives to his allies, who in turn engineered a redistricting plan that gave Republicans five more seats in Congress. His palling around with convicted lobbyist Jack Abramoff is still under investigation.

With DeLay’s departure, the Democrats lose their most convenient symbol of abuse of power by the Republican majority – but they have not lost the issue. DeLay’s successor as majority leader, John Boehner of Ohio, continues to manage the House on the same partisan basis, looking for votes almost exclusively on his own side of the aisle and declining to offer Democrats any incentives to cooperate.

And that raises an interesting challenge for the new White House chief of staff, Josh Bolten. If he is the realist that his admirers believe, he has to acknowledge the odds that there will be fewer Republicans in Congress after November than there are today – and perhaps not a majority.

In the House, Speaker Dennis Hastert is headed into what is probably his final term before retirement, shorn now of the support and day-to-day managerial muscle of the man who installed him as speaker, Tom DeLay. That means that if the Republicans maintain control, a lame-duck speaker will be working to deliver votes for a lame-duck president. That could spell an awfully difficult – and unproductive – final two years for the Bush presidency, unless the White House finds a different approach to Capitol Hill.

The old game of muscling bills through by rounding up Republican votes through a combination of political and financial force – the game at which Tom DeLay excelled – is over.