In announcing he will resign his congressional seat, Rep. Tom DeLay did one last favor for his party, strengthening the likelihood that Republicans will retain the 22nd District of Texas this November and, with it, control of the U .S. House.

DeLay cited his desire to prevent “liberal Democrats an opportunity to steal this seat with a negative, personal campaign.” But the underlying and unstated factor is the growing belief that the House GOP’s 12-year majority is in jeopardy and every single race could count.

Still, long before a mounting array of legal charges and political turmoil combined to put an abrupt end to the Sugar Land lawmaker’s tumultuous House career, he had achieved something far more lasting than victory in a single election. Largely due to DeLay’s efforts, the Texas Republican party has not only gained but probably cemented control of the state’s congressional election for the next generation. That’s the likely long-term result of the controversial redistricting plan that he helped muscle through the newly Republican state legislature in 2003.

This year, Democrats were largely concentrating on DeLay and on protecting one more threatened incumbent of their own, Rep. Chet Edwards, of Waco, while hoping that the U.S. Supreme Court will overturn part or even most of DeLay’s handiwork.

But the reaction of the justices during a hearing on the Democratic appeal last month led most court observers to conclude that was unlikely.

And even if it happens, the GOP majority that the plan created seems likely to endure for at least the next decade or two, though Democrats and some Republicans fear it could be overcome sooner if the GOP fails to attract more of the state’s growing Hispanic vote.

Besides protecting his own House seat, DeLay’s departure from the political scene removes one of the principle targets of the Democratic contention that GOP control of the White House, the Senate and the House has led to a “culture of corruption” epitomized by the burgeoning probe in which GOP lobbyist/fundraiser Jack Abramoff and at least two former DeLay aides have pleaded guilty.

But there are questions as to how deep the legal and political damage will extend within Congress. Many analysts believe that Democratic prospects in November stem more from the problems that President Bush has encountered in Iraq and his mismanagement of things like Hurricane Katrina and the Dubai port deal.

Beyond the political impact, Delay’s departure removes one of the principal architects of the success that House Republicans have enjoyed in passing many of President Bush’s initiatives despite their relatively slender majority.

In his formal statement, the congressman said he was proud of his contributions “to the conservative movement : and the enduring national conservative majority that has been transforming our nation for the past decade.”

How long that majority continues to shape national policy may be open to question, but there’s no doubt that the success Republicans have enjoyed in cutting federal taxes, along with their failure to curb overall federal spending, will continue to play a major role in setting national policy.

And it has been the House Republicans, led in large part by DeLay, who have been in the vanguard of that effort.

The DeLay legacy is not, of course, totally positive, even from a Republican viewpoint.

To his many critics, his success in melding the Republican political machine with the lobbyists of Washington’s K Street has led to a level of corruption of which Abramoff may be the worst, but perhaps not the only, example.

But the cautious way in which Congress has been approaching the question of lobbying reform suggests that very little is likely to change, other than through prosecutions of outright criminality.

Long before Republicans won control of the House, DeLay had started to make a reputation as an expert vote-counter with a good sense of the pulse of the membership. In choosing now to step down, he shows he has not lost that knack.