SALT LAKE CITY -- Utah has emerged as an improbable battleground in the fight for the future of the GOP, as the party's veteran U.S. senator -- with nary a whiff of personal or political scandal -- has become one of the most threatened lawmakers up for re-election next year.

Robert Bennett is no Northeast liberal. Raised in Salt Lake City, he built a successful business, manufacturing day-planners, that made him wealthy. His grandfather was a president of The Church of Jesus Christ of Latter-day Saints. His father served four Senate terms, meaning one or the other has held the seat for the better part of 60 years.

Yet those very attributes -- longevity, seniority -- only compound the challenge facing Bennett who, like other Republicans across the country, faces attack within the party from those who find him insufficiently conservative.

As last week's elections showed, the 2010 campaign is shaping up as another driven by a deep, throbbing anger against the political establishment. President Barack Obama has been a prime target at rowdy town hall meetings and "tea party" protests, and Democrats certainly have much to fear, as they hold the majority in Congress. But the free-floating hostility may pose a danger to members of both parties.

"This is not a Democrat problem. It's not a Republican problem. It's an incumbent problem," said Cherilyn Eagar, one of three Republicans, so far, taking on Bennett. "It's on both sides of the aisle."

A national poll issued this week reflected that sentiment. Only about half of the registered voters interviewed, 52 percent, said they would like to see their representative re-elected next year, among the most negative findings in two decades of Pew Research surveys.

As Bennett seeks a fourth term, Eagar and others, boosted by the conservative Club for Growth, cite his extended time in Washington and criticize his willingness to work with Democrats on issues such as health care reform and the Wall Street rescue approved amid last year's financial crisis.

"People are fed up with the way Washington has historically conducted its business: horse-trading and giving this to get that," said Tim Bridgewater, another Republican running.

The insurgency is not limited to Utah. In several states, Senate hopefuls on the right have taken on comparative moderates preferred by GOP insiders, who consider them more electable.

In California, former Hewlett-Packard executive Carly Fiorina, bidding to face Democratic Sen. Barbara Boxer next year, faces Irvine Assemblyman Chuck DeVore, who is rallying support from conservatives nationwide. In Florida, Gov. Charlie Crist is fighting a stiff primary challenge from former state House Speaker Marco Rubio.

"One side feels the Republican Party has lost its way and sacrificed its basic principles," said Jennifer Duffy, who tracks Senate races for the nonpartisan Cook Political Report. "The other thinks the party has moved too far right and become inflexible and intolerant."

That worries some Republicans in Utah, which has not elected a Democratic governor in nearly 30 years, or a Democratic senator in nearly 40. Last week, a traditionally GOP House seat in upstate New York went Democratic, thanks largely to party infighting driven by nationally prominent conservatives.

Rep. Jim Matheson, a popular Democrat who represents parts of Salt Lake City, its suburbs and a good chunk of rural Utah, has ruled out a Senate bid, to the relief of GOP insiders. "But if it looks like Republicans are totally killing themselves and he can walk into the seat, I believe he'll switch and put the race in play," said Dave Hansen, Utah's GOP chairman.

For now the focus is on Bennett. He has already spent more than $500,000 -- exceeding what some entire Utah congressional races cost -- and aired his first TV ads. Bennett did not run a single spot in 2004, when he easily won re-election.

Critics have taken to the air as well. The Club for Growth, which funneled about $1 million into the New York race, has aired spots criticizing Bennett's sponsorship of bipartisan health care legislation, even though it has gone nowhere. "We see this bill as pretty much a massive government takeover," said David Keating, the group's executive director.

Bennett rejects that assertion -- his bill would create a private insurance system of state-based purchasing pools -- and independent fact-checkers back him up. Still, Keating's group has launched a letter-writing campaign targeting grass-roots activists, who hold considerable sway under Utah's unusual nominating system.

Republicans will vote for their nominee at a May convention. If a candidate fails to garner 60 percent support, the two top finishers will advance to a statewide June runoff. Utah Republicans are generally very conservative; convention delegates are likely to be more conservative still.

Bennett's opponents, like the senator, profess to abhor taxes, big government and excessive regulation, though they go much further, denouncing Obama's policies as a socialist threat to the country. Bennett dismissed socialism as "a buzzword" that inflames emotions but distracts from the more serious problem of structural deficits

He defends his support for the Wall Street rescue -- "I still believe it was the right vote" -- recalling how one senator likened the urgent atmosphere to a James Bond movie: "The world coming to an end if we don't act in the next 24 hours."

The senator's opponents call the bailout a costly government overreach. Bridgewater, a two-time congressional candidate, said he would have rejected the rescue effort, regardless of a possible economic collapse. "Capitalism isn't always rosy," he said. "Down cycles have to be allowed in order for the inefficiencies to be worked out."

Since his vote last fall, Bennett has opposed virtually the entire Obama agenda, including the economic stimulus plan, the auto industry bailout and the second half of the $700 billion rescue fund, which required follow-up approval. Still, those moves don't address two of Bennett's biggest problems: his professorial manner -- which some find off-putting -- and the fact he is seeking a fourth term after promising to serve just two.