WASHINGTON - A wartime president with sky-high popularity. A campaign cash advantage for Republican candidates. A failure by Democrats to articulate a clear alternative vision.

Those were some key factors behind the historic - and unexpected - Republican triumph in Tuesday's election, politicians in both parties said yesterday.

"You cannot ignore the fact that America did change on 9/11, over a year ago. And I think that did have an effect on this election," said Republican Sen. Trent Lott of Mississippi, who will soon reclaim the title, and power, of Senate majority leader.

President Bush, by campaigning all-out in the final days of the campaign, "put his prestige on the line, and I believe it made a huge difference in the election," Lott added.

For the first time ever, Republicans gained House seats in the middle of a Republican president's term.

In an even more impressive - and unexpected - comeback, Republicans regained control of the Senate, which they had lost to the Democrats last year after Vermont Sen. James M. Jeffords defected from the Republican Party. This time, they got some breathing room; instead of a 50-50 split, as they had before Jeffords bolted, they'll have at least a two-seat Senate edge.

An Election Day poll by one Republican survey firm concluded that Bush had "transformed this election." A strong pro-Bush tilt among late-deciding voters helped produce a Republican surge and a 6-point Republican advantage in House races, according to Public Opinion Strategies.

Democratic National Chairman Terry McAuliffe tried to play down the results, attributing his party's House and Senate setbacks to the "political muscle that carried many Republicans over the finish line" and to "a wartime president with the highest sustained approval ratings in history."

Like other Democrats, McAuliffe said the two parties still are "basically [in] the same place we were after the 2000 election. At 50-50. Parity. Not much has changed."

In fact, though, the atmospherics in Washington were drastically altered by this week's vote. The mood swing was evident in the sudden contrast between the Republicans' elation and the downbeat tone of Democrats and their allies.

While Bush remained out of sight at the White House yesterday, perhaps to avoid being seen gloating in public, Democrats began taking aim at each other. Rumors swept Capitol Hill of a possible shakeup in both the House and Senate leadership.

Democratic Rep. Harold Ford of Tennessee, a longtime ally of former Vice President Al Gore, hinted openly at the need to replace Rep. Richard A. Gephardt as House Democratic leader.

Gephardt acknowledged that "obviously, we're all responsible" for what happened. The congressman from St. Louis is likely to announce his candidacy soon for the 2004 Democratic nomination.

Though he had been expected to hold on to his party leadership position, at least through the early phase of a presidential run, he is now going to relinquish that job instead.

Senate Majority Leader Tom Daschle, also expected to announce soon whether he'll be a presidential contender, is being downgraded to minority leader as a result of his party's loss of Senate control.

At AFL-CIO headquarters, a downcast President John Sweeney said the Democrats had failed to be "crystal clear about what they stand for" on issues of importance to workers - jobs, the economy and health care - and had not presented a clear alternative to the Republicans.

Democrats "were no match for the president's focus on Iraq," said Sweeney, whose unions spent $62 million, by their own estimate, helping mainly Democratic candidates.

The lesson of this week's results was that Democrats "have to have a strong economic message for 2004," said the labor federation chief.

Among campaign insiders, the biggest winner in Tuesday's voting, other than Bush, was his political strategist, Karl Rove. The White House aide decided where Bush would go to raise money and campaign for Republicans over the past year.