On Tuesday, the middle rebelled.

Results of the midterm elections suggest that the famous Karl Rove strategy of keeping power by energizing the GOP base with wedge issues may have outlived its usefulness. Democrats took control of the House and apparently the Senate, exit polls suggest, largely by running moderate candidates - and speaking to the concerns of disaffected independents and swing voters.

Independents voted for Democrats by 59 percent to 37 percent, the exit polls showed. GOP Senate candidates, for instance, won among independents only in New Jersey and Rhode Island.

"This is a victory for the vital center of American politics over the extremes," said Al From, founder of the centrist Democratic Leadership Council. "In the last six years, Republicans have deliberately abandoned the political center and invited Democrats to occupy it."

Fealty to the conservative base has marked President Bush's approach to governing and politics, with his chief political strategist, Rove, asserting that a permanent Republican majority could be built by cultivating core supporters and a superior turnout operation.

Bush solidified his support in the aftermath of the Sept. 11 attacks, when the public was largely convinced that the GOP was the best guardian of the nation's security. In his 2004 reelection campaign, Bush used issues such as gay marriage and abortion to stimulate turnout of socially conservative voters in key states such as Ohio.

Democrats, through activist groups such as MoveOn.org, learned how to practice base politics themselves, and the electorate has grown steadily more polarized.

But with growing disillusionment about the occupation of Iraq, pre-election polls this year showed that voters no longer accepted Bush's contention that the battle there was central to stopping terrorists, and his party began losing its advantage on security. Social issues did not outweigh concerns on the war and economic issues.

If weariness with war and congressional scandal opened the door, Democratic candidates were talking about issues that mattered to voters in the middle, including economic uncertainty, the need to extricate the United States from Iraq, and stem-cell research.

While the exit polls also showed a fired-up Democratic base, "the key to the victory was in the contested center of the electorate, among moderates, independents, middle-class voters, and suburbanites," From said.

CNN political analyst William Schneider said the big break of independents toward Democrats was a first. "We haven't seen that big a vote for one party among independents since exit polling began about 30 years ago," he wrote on CNN.com. "For about the last 10 years, the swing voters have divided evenly . . . This year they really had their revenge."

The split was particularly acute in Pennsylvania's Senate race, where 71 percent of independents supported Democrat Bob Casey Jr., to 29 percent for defeated Republican Sen. Rick Santorum.

Democrats won voters who described themselves as "moderates" in every Senate race and eight out of 10 of the most competitive governor's races.

Neil Oxman, the Philadelphia-based strategist who worked on Gov. Rendell's reelection campaign, said independents vented their anger on Republicans for the war, the poor response to Hurricane Katrina, a period of $3-a-gallon gas, and congressional scandals.

"It was explosive," Oxman said. "They were saying to these guys in power: `Rethink things. Stop being so doctrinaire and single-minded.'"

The resurgent moderate voter could have ramifications for the 2008 presidential race, analysts and strategists say. Democrats' challenge will be to keep the independents they have attracted, while Republicans will search for ways to get them back.

"It would be my hope that the party will learn from the experience of yesterday and broaden its approach and move away from ideology to pragmatism," Pennsylvania's Sen. Arlen Specter said. "It depends on how my Republican colleagues respond to what happened . . . You have to do more than listen. You have to hear them."

In Virginia, the Associated Press contacted election officials in all 134 localities where voting occurred and said Democratic challenger Jim Webb was leading incumbent Sen. George Allen by 7,236 votes, which would give Democrats their 51st seat in the chamber. But Allen had not yet conceded.

In Specter's view, if the Republican Party ends up losing control of the Senate, much of the blame would rest on the stem-cell issue. Sen. Jim Talent, R-Mo., lost reelection in part because of his opposition to a state ballot initiative supporting research on embryonic stem cells.

Talent and religious conservative voters feared the research would lead to human cloning and increase the number of abortions. But moderate voters saw the promise of cures for dread diseases, and the measure passed narrowly. The victorious Democrat, State Auditor Claire McCaskill, supported the measure.

The endorsement of stem-cell research was only one message from heartland voters. They defeated a ban on abortions in South Dakota and rejected a ban on same-sex marriage in Arizona.

"Some of what we're seeing here is a shift from a lot of the wedge issues to kitchen-table issues and issues of national interest, like the war," said Eric McFadden, field director of Catholics in Alliance for the Common Good, a group working to turn out Catholic moderates.

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