Utah Sen. Bob Bennett will likely know the fate of his political future by tomorrow, when the state Republican Party holds its nominating convention. It's an interesting twist that in a year when the political winds are at the backs of Republicans nationwide, an entrenched GOP incumbent is facing his most challenging re-election -- in the primary.

It's evidence that voter frustration isn't necessarily a partisan issue. In fact, Bennett is one of five Senate incumbents facing stiff primary challengers: Republicans include Bennett and Arizona's John McCain; Democrats are Colorado's Michael Bennet, Arkansas's Blanche Lincoln and Pennsylvania's Arlen Specter, who left the GOP to escape a competitive challenge and found another one awaiting him.

That's a relatively high number of incumbents facing legitimate primary challenges, and other establishment-backed challengers across the country are having similar trouble clearing the path for their party's nomination.

"It's a combination of two things: the overall environment and a sort of unrest in both parties," said Jennifer Duffy of the Cook Political Report. "Obviously the focus has been on the GOP and Tea Parties, but there has been evidence of progressives not being happy as well."

Like Bennett, the judgment days for Specter and Lincoln could come this month, with both preparing for May 18 primaries. Even if they win, they'll also face competitive general election races.

As for Bennett, he's up against challengers from the right and a nominating system that puts him at a distinct disadvantage. 3,500 delegates elected in neighborhood caucuses around the state are descending upon Salt Lake City tomorrow for a three-round voting process that could determine the Republican nominee. It puts a great deal of power in the hands of a select group of people.

"Utah has the most exciting Senate race in the country, and less than 1 percent get to vote in it," said Kirk Jowers, director of the Hinckley Institute of Politics at the University of Utah. "Republican voters in general are not that upset with Sen. Bennett. He would probably win the primary handily and the general election by 30 or 40 points."

Bennett's top competitors, according to recent polling of the delegates, are attorney Mike Lee and businessman Tim Bridgewater. The top three candidates make it to the second round of voting, and the top two go to the final round. If one candidate receives 60 percent of the vote, they become the nominee. Otherwise the top two face off again in a June 22 primary.

According to Mason-Dixon managing director Brad Coker, the make-up of the delegates is mostly male and very conservative. Indicative of the overall mood of the delegates: In one poll Coker conducted, seven-in-10 said they wouldn't have re-nominated the state's other Republican senator, Orrin Hatch, who was re-elected in 2006.

Coker believes that if Lee and Bridgewater make it to the final round of delegate voting, neither will get the 60 percent necessary to avoid a primary. However, if Bennett makes it to the final round, Lee will win the nomination outright.

"I'm fairly convinced Bennett won't come out of the convention," Coker told RCP.

The potential ouster of Bennett is partly due to his legislative work and voting record, which the Almanac of American Politics describes as moderate-to-conservative. Jowers said delegates mainly list three things they're upset with Bennett over: his TARP vote, the Bennett-Wyden health care bill and his support for earmarks.

There's also a feeling that it's simply time for someone new, as Bennett's held his father's former seat since 1992. Among those ready for a change are former Gov. Norm Bangerter and former Rep. Jim Hansen, both of whom endorsed Lee over Bennett.

"Bob Bennett is a very articulate, intelligent, analytical man. He's a very good man," Hansen told RCP. "He's also quite old, like I am. I would like to see a younger, dynamic, well-trained, extremely intelligent and well-qualified person move into the Senate."

Hansen, who served 22 years in the House, has known Bennett a long time -- he sat behind Bennett in high school English class "100 years ago," as Hansen put it. But his decision to back another candidate aligns him with Tea Party supporters who make up two-thirds of the convention delegates, according to a recent Mason-Dixon poll.

State Rep. Ken Sumsion endorsed Lee as well. However, if Lee goes down in the early rounds, Sumsion told RCP he'd be happy to support someone else -- just not Bennett.

"He's flat out arrogant," said Sumsion, who named the same arguments against Bennett that Jowers listed, as well as several others. "He's had plenty of time to improve things, and our nation is going in the wrong direction. Many of my constituents feel the same way."

"We want new blood, fresh ideas and fresh energy," he added. "I want a U.S. senator that isn't going to make a career out of it."