PROVO — Nearly 40 percent of registered Republican voters in Utah's 3rd Congressional District are undecided with Tuesday's primary between incumbent Chris Cannon and challenger John Jacob just days away.

Cannon is running television ads and both candidates are scrambling to line up influential endorsements even though it is unlikely they can change the minds of most voters or effectively craft messages to the undecided voters, consultants with both campaigns said while discussing their strategies Wednesday during a Public Relations Society of America luncheon in Provo.

"Our polls show that 38 percent haven't decided who to vote for," Jacob press secretary Hayden Hill said after the lunch.

Cannon campaign manager Nathan Rathbun confirmed during the event that a large bloc of voters are undecided, but he and Hill agreed the Cannon-Jacob race would boil down to how well the two campaigns do at getting voters who have chosen their candidates to go to the polls on Tuesday.

"This election will be won or lost based on who does better getting their voters out to vote," Rathbun said.

The turnout for the early summer primary is expected to be low, between 13 percent and 18 percent. For Jacob, the lower the better, with the hope that Cannon supporters would stay home while Jacob backers, energized by his challenge, would then cast enough ballots to push the election his way.

Cannon launched his television ad campaign Sunday night with commercials on three Salt Lake City stations. The spots have run on local cable during breaks on Fox News Network and CNN.

Cannon also has a new radio spot that slams national immigration reform groups for "their vicious smear campaign" against him. Those groups, mainly Team America, which is running a radio ad ridiculing Cannon for saying he is tough on illegal immigration, want Cannon replaced by Jacob, who they believe is stronger on the issue.

Jacob and others have tied Cannon to a Senate bill that creates a path to citizenship for illegal immigrants. They have complained that it is similar to a bill Cannon backed two years ago.

Rathbun said Wednesday that Cannon is against any path to citizenship for illegal immigrants. Instead, Cannon supports legislation that would create a guest-worker program that would allow some illegal immigrants to remain in the country for up to three years. The program would be extendable but would not provide an opportunity for citizenship, Rathbun said.

Jacob and others have called that an amnesty. Cannon has said it is not because it does not allow for citizenship and would likely require those who qualified to return to their native country at some point in the process.