WASHINGTON - Embattled Democratic Sen. Blanche Lincoln of Arkansas narrowly won nomination to a third term Tuesday night, overcoming a labor-backed challenger and defying a nationwide anti-establishment tide. California Republicans turned to a pair of wealthy businesswomen, first-time candidates Meg Whitman and Carly Fiorina, to lead their party into the fall campaign.

On the busiest night of the primary year, tea party activists flexed their muscle in South Carolina, pushing state Rep. Nikki Haley ahead of three rivals in the Republican gubernatorial race. Shy of a majority, she will face Rep. Gresham Barrett in a June 22 runoff.

Another tea party-backed contender, Sharron Angle, led a crowded field for the right to challenge Senate Majority Leader Harry Reid of Nevada in the fall.

In the marquee race of the night, Lincoln had 52 percent of the vote in nearly complete Arkansas returns, to 48 percent for Lt. Gov. Bill Halter.

The result marked a stunning defeat for organized labor, which had poured more than $5 million into an effort to dump Lincoln in retaliation for her departure from party orthodoxy on numerous issues. Seemingly headed for defeat in the race's final days, she unleashed a campaign ad that acknowledged voter anger with Washington, and she also got a boost from former President Bill Clinton, who told voters that out-of-state unions were trying to steal their votes.

Lincoln will meet GOP Rep. John Boozman in November in a race that national Republicans have targeted.

Nearly two decades after California Democrats helped fashion a "year of the woman" in national politics, Republicans served notice they hope to turn the tables.

Whitman, the former CEO of eBay, lapped a crowded field of rivals, and her fall opponent will be former Gov. Edmund G. Brown Jr., who served two terms before leaving office in 1983.

California Republicans tapped Carly Fiorina, a former CEO of Hewlett-Packard, to challenge three-term Democratic Sen. Barbara Boxer in the fall. Victories by Boxer and fellow California Sen. Dianne Feinstein were standout events of the 1992 elections that sent record numbers of women to Congress, many of them Democrats.

At least two incumbents did not fare as well as Lincoln on Tuesday.

Republican Gov. Jim Gibbons of Nevada fell to Brian Sandoval, a former federal judge, after a term marked by a messy public divorce and allegations of infidelity. Rory Reid, the son of the Senate majority leader, won the Democratic nomination.

And Republican Rep. Bob Inglis of South Carolina trailed challenger Trey Gowdy by double digits, though he qualified for a runoff on June 22 in the solidly conservative district. The challenger campaigned as an opponent of the 2008 financial bailout legislation that the incumbent supported.

The day's races took place in the shadow of the worst recession in decades, stubbornly high unemployment, dispiriting day-by-day images of the damage caused by an offshore oil rig disaster and poll after poll that reported the voters angry and eager for a change.

Gibbons was the first governor tossed from office in a year of living dangerously for incumbents everywhere.

With her win and his run-off, Lincoln and Inglis avoided joining a list of congressional incumbents sent packing by voters in their own party in earlier contests - Sens. Bob Bennett, R-Utah, and Arlen Specter, D-Pa., and Reps. Alan Mollohan, D-W.Va., and Parker Griffith, R-Ala.

"I don't believe very many politicians or very many people on the political scene, so I just had to vote my conscience and my prayers," said Judy Hamilton, a 59-year-old administrative assistant from Columbia, S.C., as she cast her ballot in the state's Republican primary.

That sentiment made the day's balloting a prelude to the fall, when Republicans hope to challenge Democrats for control of Congress and the two parties vie for three dozen statehouses midway through President Barack Obama's term.

In a pair of Virginia congressional districts likely to become fall battlegrounds, Republicans chose Scott Rigell and Robert Hurt to challenge Democratic freshmen Reps. Glenn Nye and Tom Perriello.

And in Georgia, Republican Tom Graves, running with tea party support, won a special election to fill out the final few months left in the term of former GOP Rep. Nathan Deal. who resigned to run for governor.

Lincoln's triumph suggested a path to victory for incumbents under duress everywhere - identify and focus on a force even less popular than incumbency.

In her case, organized labor made a perfect target, particularly in a state with low union membership. "The vote of this senator is not for sale and neither is the vote of the people of Arkansas," she said during her victory party at Union Station in Little Rock.

It was a point Clinton made in a speech in May that was incorporated into a television commercial. "This is about using you and manipulating your votes," the former president said to voters of the state that five times elected him governor.

In South Carolina, Haley battled several rivals as well as claims that she has had trysts with two men. She vociferously denied the allegations of infidelity and relied on support from tea party activists and an endorsement from former Alaska Gov. Sarah Palin to aid her in the race with Barrett, Lt. Gov. Andre Bauer and state Attorney General Henry McMaster.

In California, Brown had little opposition for the Democratic nomination to reclaim an office he left in 1983. Not so Whitman, who overcame Insurance Commissioner Steve Poizner in a battle of multimillionaires. She spent more than $70 million of her own fortune, while he put in more than $25 million.

In the California Senate primary, Fiorina's leading rivals were former Rep. Tom Campbell and state Assemblyman Chuck DeVore.

In Iowa, Branstad, who served four terms as governor before leaving office in 1999, triumphed easily over two candidates and will face Gov. Chet Culver in the fall.

In the House, incumbents sought renomination in 92 congressional districts, and few had serious opposition.

In South Carolina, Rep. Tim Scott led a crowded field seeking the Republican nomination for Congress. If elected, he would be the party's only black member in the House. His rival in a June 22 runoff is Paul Thurmond, son of the late Sen. Strom Thurmond, who once sought the White House on a platform of racial segregation.

Associated Press writer Andrew DeMillo in Little Rock, Ark., contributed to this report.