WASHINGTON -- For Senate Republicans, 2012 is starting a lot like 2010.

They have a shot at taking control away from Democrats as long as insurgent conservatives who are defeating the party's more establishment candidates in primaries don't frighten too many independent voters like they did two years ago.

Deb Fischer, a little-known state senator, became the latest unexpected Senate GOP nominee Tuesday, rallying late to upset the favored – and better funded – choices of both the party's mainstream and tea party establishments: Nebraska Attorney General Jon Bruning and state Treasurer Don Stenberg.

Her victory occurred just a week after tea party and other conservative groups embraced Indiana state Treasurer Richard Mourdock, who scored an arguably bigger upset – knocking off six-term Sen. Richard Lugar, the Senate's longest-serving Republican.

The message for the GOP: Insurgents are back.

What's yet to become clear is whether they exemplify 2010's class of conservative upstarts – Florida's Marco Rubio, Kentucky's Rand Paul, Utah's Mike Lee and Wisconsin's Ron Johnson. All were early underdogs in the primary season and are now U.S. senators.

Or will the 2012 class turn out to be more like Christine O'Donnell in Delaware, Sharron Angle in Nevada and Ken Buck in Colorado? They, too, emerged from relative obscurity to defeat more established Republicans early in the election season, only to stumble later and cost the GOP three seats many thought it should win.

Once again the GOP will rely on lesser-known candidates in key races. The seats in Indiana, currently held by the GOP, and Nebraska, a pickup opportunity, represent must-wins if Republicans are to have any chance at capturing the Senate majority. They need a net gain for four seats to take control – three if a Republican also wins the White House.

While the GOP establishment has the presidential candidate it wanted in former Massachusetts Gov. Mitt Romney, the jolts to its strategy for winning the Senate may not be over.

In Missouri, three Republicans are vying to take on vulnerable Democratic Sen. Claire McCaskill. Among them is John Brunner, a businessman who has never run for office before. In Wisconsin, former Gov. Tommy Thompson is the big-name Republican running for a seat the GOP is trying to flip, but he faces a number of lesser-known, more conservative challengers. In Arizona, six-term Rep. Jeff Flake is the favorite to get the GOP Senate nomination, but he is being challenged by wealthy businessman Wil Cardon, who casts himself as the tea party candidate and accuses Flake of being a Washington insider.

For now, Republicans say they're optimistic 2012 won't mirror 2010 in the end. Where O'Donnell, Angle and Buck all stumbled, Republicans say a more polished group of insurgents is emerging this year.

"What the victory of someone like Mourdock shows is that the tea party still has the energy and that's a valuable strength for Republicans," said Jeff Berkowitz, a GOP consultant. "But it also shows the movement has matured. He has great credentials, he has a track record and he is a statewide official."

Berkowitz said the same applies to Fischer, whose credentials – she's a two-term state senator and a rancher – make her a plausible nominee.

Democrats say the GOP is simply spinning primary results that will actually make it harder for them to win in November. Party officials have been quick to label both Fischer and Mourdock as novices and too conservative, arguments that worked well against O'Donnell, Angle and Buck in 2010.

Within minutes of Fischer's victory in Nebraska, the Democratic Senatorial Campaign Committee sent out an email calling her the "accidental candidate."

"These results set up a promising general election match-up between Bob Kerrey, a proven independent leader, and Deb Fischer, an untested hypocritical politician whose record and positions have never been scrutinized," said Matt Canter, a spokesman for Senate Democratic campaign arm.

Kerrey, a former governor and two-term senator, is the Democratic nominee in Nebraska, returning to the state after 10 years as a university president in New York City. In Indiana, Democratic Rep. Joe Donnelly is the party's Senate nominee after two terms representing a swing district in the House.

Fischer and Mourdock, however, are different candidates from O'Donnell, Angle and Buck.

Mourdock is a former geologist who ran for office several times before being elected state treasurer in 2006. He's now won two terms in statewide races and endeared himself to the state's most conservative voters after challenging Chrysler's bankruptcy bailout in a case that reached the U.S. Supreme Court. He also survived an onslaught by Lugar, who spent millions on ads attacking him. Democrats contend that his stance on the Chrysler bailout will hurt him in a state with a large force of auto industry workers.

Fischer used her background to her advantage, playing up a "ranch girl" persona." But she scoffs at the idea that she's a political novice.

"Some folks seem to think I came out of nowhere in this race," she said. "I have been a state senator for eight years. But more importantly than that, I've been involved in a number of organizations in the state for 30 years. I'm not an unknown."

Nebraska Gov. Dave Heineman, one of the state's most popular Republicans, calls Fischer "one of the most effective lawmakers we've ever had."

Local Democrats say the party would be foolish to dismiss her, even if she is deeply conservative.

"So many times, I've called her the Michele Bachmann of Nebraska, but she won't say stupid things like Bachmann has," said Democratic Party donor Bud Pettigrew, referring to the former presidential candidate and Minnesota congresswoman.

Pettigrew, who also is a neighbor of Fischer's, adds: "I don't like her ideas, but I'm not going to underestimate her. She's extremely intelligent."

However Fischer and Mourdock fare in November, Republicans say it's a bad season for longtime officeholders.

"If you're an establishment figure, whether it's (former French President Nicolas) Sarkozy or an establishment Republican in Nebraska, you're in trouble," said Alex Castellanos, a Republican consultant.

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Associated Press writers Margery Beck in Omaha, Neb., and Grant Schulte in Lincoln, Neb., contributed to this report.

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Follow reporter Henry C. Jackson on Twitter (at)hjacksonap

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