Sen. Bob Bennett (R-Utah), campaigning for his life as he seeks to sway skeptical Republican delegates in his home state’s unusual primary election system, has spent less and less time voting in Washington as Saturday’s nominating convention in Salt Lake City draws closer.

Bennett hasn’t cast a Senate vote since April 22, and according to Congressional records the third-term Republican has missed 25 percent of votes this year — the chamber’s third-worst attendance record. The Utah Republican primary system grants power to individual state GOP delegates, and Bennett’s unpopularity with this group has forced him to spend extra time at home persuading them not to toss him.

Bennett’s decision to keep close to home campaigning has not gone unnoticed in a chamber where this year the average voting rate among Members is 97 percent. But because the burden for producing 60 votes and overcoming filibusters is on the Democrats, Bennett’s absence has not had a major impact on the Republicans’ strategy.

Senate Minority Whip Jon Kyl (R-Ariz.), who is tasked with counting votes, said Bennett has kept the GOP leadership apprised of his campaign schedule. “It doesn’t cause me any problems as Whip,” Kyl said Monday.

Bennett’s Senate office conceded that the Utah Republican has been away from Capitol Hill to campaign. But spokeswoman Andrea Candrian noted that Bennett has missed just 2 percent of all votes since he first arrived in 1993, a record that she described as “outstanding” and rivaling any of his colleagues. Bennett is scheduled to spend the rest of this week on the campaign trail.

“Sen. Bennett has been splitting his time between his work in Washington, D.C., and campaigning in Utah. The majority of the votes he has missed were within a two-week time span leading up to critical events in his Senate race,” Candrian said. “The entire time he has been in touch with Republican leadership regarding which votes he needs to be present for.”

As of Wednesday, Bennett had missed nine out of the past 10 Senate roll-call votes, bringing his total of missed votes this year to 32. He missed more than a week of voting in March while at home to campaign, including 15 consecutive votes — among them a key procedural vote on the health care reform legislation that President Barack Obama has since signed into law.

Last week, Bennett missed the three cloture votes on the financial reform package. Only two Senators have a worse participation record than Bennett in 2010: Sens. Robert Byrd (D-W.Va.) and Johnny Isakson (R-Ga.), both of whom have had health problems.

Bennett is Minority Leader Mitch McConnell’s (R-Ky.) closest ally and acts as a special adviser to the GOP leadership. Bennett’s campaign has received $5,000 from McConnell’s leadership political action committee and $41,000 from the National Republican Senatorial Committee.

Given the strong anti-Washington sentiment among Utah’s GOP delegates this year, support from his Senate colleagues for his re-election bid could do more harm than good. Just two years ago, incumbent Rep. Chris Cannon managed to survive the nominating convention, only to lose the statewide Republican primary election to now-Rep. Jason Chaffetz by nearly 20 points.

“We’re certainly keeping an eye on it and wish him the best,” said McConnell, who faced a tough re-election bid of his own in 2008.

The Utah Republican nominating convention will take place Saturday at Salt Lake City’s Salt Palace. Under the format, a candidate can avoid the June 22 statewide primary election by earning 60 percent of the delegate vote at the gathering. If that doesn’t happen, the top two finishers face off.

Based on the results of elections held to determine the field of 3,500 state party delegates, Bennett could be in trouble in the crowded Senate Republican primary field. In those contests, held throughout Utah earlier this year, delegate candidates who committed to supporting Bennett at Saturday’s convention did not fare well. Bennett’s problem with Utah’s Republican base stems in part from his vote in favor of the Troubled Asset Relief Program, derisively referred to as the Wall Street bailout bill, in 2008.

A public opinion poll of rank-and-file Republican primary voters commissioned by the Salt Lake Tribune and released Sunday found Bennett leading the field with 39 percent, followed by attorney Mike Lee with 20 percent and businessman Tim Bridgewater with 14 percent. However, the newspaper also polled state party delegates, who gave Bennett just 16 percent of their support.

Saturday’s convention will feature three rounds of voting, with candidates eliminated along the way until there are two candidates remaining who have garnered the support of at least 40 percent of the delegates. Accordingly, Bennett is campaigning to be each delegate’s first or second choice. Republican operatives familiar with the race for votes liken the process to the Iowa presidential nominating caucuses, only more personal.

“Bennett has to spend a lot of one-on-one time with delegates. He just cannot afford to be in Washington,” one Republican strategist said. “The system is so bizarre. It’s clear that if this were just a regular primary, he’d be fine. It wouldn’t be easy, but it’s the uniqueness of this system that puts Bennett at particular disadvantage.”

John McArdle and Rachel Bloom contributed to this report.