Now in his sixth term, Cannon is staring down the barrel of his most serious challenge of his political career as Republican faithful meet Saturday to choose their favorite in the 3rd Congressional District.

Cannon is being challenged by David Leavitt, the former Juab County attorney and brother of former Utah governor and current Health and Human Services Secretary Mike Leavitt; and Jason Chaffetz, the former chief of staff to Gov. Jon Huntsman Jr.

It is the first time that Cannon has been confronted with well-financed and politically experienced candidates, and delegates to the state convention are being pulled hard in three directions.

"I've always struck with Chris," said Kerry Jorgensen, a state delegate from South Jordan. "I entered this thing thinking I was going to vote for him but . . . I've kind of cooled on that."

Jorgensen said he is now leaning toward Leavitt.

State delegate Michelle Hollist has met with each of the candidates, but hasn't made up her mind yet.

"It's definitely between Mr. Cannon and Mr. Leavitt, and I guess what I'm deliberating at this time is how much is Mr. Cannon's seniority an issue as opposed to getting fresh ideas in there," she said.

This marks the third time Cannon has faced a Republican challenger, each time posing a more serious threat. All three ended in primaries and Leavitt says this year will be no different.

Last week, President Bush wrote a letter endorsing Cannon, calling him a strong representative who should be re-elected. That backing in a district where Bush remains popular makes it unlikely that Cannon will be knocked out Saturday, said Leavitt.

"There will be a primary election in this race. It's inevitable in my opinion," Leavitt told a group of state delegates meeting at a pancake house in Riverton this week. "That letter pretty much guarantees Chris' spot in the primary."

That means if delegates want a change, they have to pick a candidate who has a campaign staff, an organization and $500,000 to spend, said Leavitt, who has spent about $40,000 of his own money on the race and says only he can beat Cannon.

"If Jason Chaffetz beats me [at convention], Chris Cannon will be the congressman. Jason Chaffetz has no resources, no organization," Leavitt said.

Chaffetz, who has been outspent by his opponents many times over, says his grassroots support will prevail.

"If we're truly going to elect a fiscal conservative, we should elect one that acts like it and how sad that [Leavitt] thinks viability depends on one's ATM account," he said. "This election is not for sale and people are fed up with it, and so am I."

Chaffetz took the unusual step of buying ads that started running on cable TV last week. He predicts he could get support from 60 percent of delegates to avoid a primary.

Former airline pilot Joe Ferguson and Stone Fonua are also seeking the GOP nomination.

Joe Hunter, Cannon's chief of staff, says the congressman runs into challenges because he isn't a member who "plays to a political audience."

"He actually has issues that he feels strongly about and that's what he focuses on," Hunter said. The attention to Cannon's immigration record, which Hunter said has been distorted, has been a particular factor in recent elections.

And the 3rd District is a "very politically vibrant part of Utah," he said, which has produced better funded, more aggressive opponents.

While the challenge to Cannon is the marquee matchup, other contested races will also be decided, including a showdown in the State Treasurer's race between Richard Ellis, the deputy treasurer, and state Rep. Mark Walker.

Six Republicans are vying for the 2nd District nomination and the right to challenge Democratic Rep. Jim Matheson. And Huntsman is facing token resistance in his re-election bid.