SALT LAKE CITY — A last-minute push to get unaffiliated voters to sign up as Republicans at the polls Tuesday so they can vote in the 3rd Congressional District primary election could delay the final results in the race.

"There will be a portion that will be delayed," Utah County Clerk/Auditor Bryan Thomson said, predicting there could be as many as 15,000 ballots cast that won't be counted for at least a day.

It's another problem resulting from Utah County mistakenly sending more than 68,000 unaffiliated voters in the 3rd District Republican ballots in the first primary largely being conducted by mail that also includes nonpartisan municipal races.

The Republican Party closes its primary elections to nonmembers, making the race between Provo Mayor John Curtis, former state lawmaker Chris Herrod and political newcomer Tanner Ainge off-limits to unaffiliated voters.

Thompson's office sent the unaffiliated voters a postcard telling them they couldn't vote in the GOP primary in the race to replace former Rep. Jason Chaffetz, although their votes in any nonpartisan municipal races also on the ballot would be counted.

The postcard also told those who planned to join a political party that they had to bring their "unvoted ballot to surrender" to the polls on Election Day in order to vote as a member of that party.

Several organizations, however, claim that even those unaffiliated voters who already cast a ballot should be able to show up at a voter service center Tuesday and vote again as Republicans by joining the GOP.

The organizations, Mormon Women for Ethical Government, Salt Lake Indivisible and Action Utah, are holding a rally at noon Monday at the Utah County Courthouse to clear up what they're calling confusion surrounding the primary.

State Elections Director Mark Thomas said he agrees that unaffiliated voters should be able to cast a provisional ballot as Republicans even if they're already voted because Utah County sent them a ballot with the 3rd District race listed.

"We know there's potential for some voters, unaffiliated voters, to say, 'Oh, well, I wanted to affiliate at the polls,'" and when they received a ballot with the GOP race on it, "thought, 'Oh, I'll just fill this out and submit it," he said.

Thomas said he has been assured only the ballots cast on Election Day by voters who choose to join the GOP will be counted in Utah County, not any ballots they previously mailed in as unaffiliated voters.

GOP ballots also wrongly went out to some unaffiliated voters in Wasatch County, but none were in areas with nonpartisan races. The 3rd District includes parts of Utah and Salt Lake counties, and Carbon, Emery, Grand, San Juan and Wasatch counties.

"It is an unprecedented mess, this special election. It really is," said Sharlee Mullins Glenn of Mormon Women for Ethical Government.

Glenn said the nonpartisan group is not trying to help any of the candidates running.

"This event on Monday is about educating voters, promoting civic engagement, and making sure that everyone who is eligible to vote in this unprecedented election knows that they are able to," she said.

It's needed, Glenn said, "particularly because of the confusion surrounding unaffiliated voters this election. This is not in any way a partisan event, nor is it an attempt by 'liberals' to get votes for a more 'liberal' candidate."

Social media posts about the event urge participants not to bring campaign signs for any specific candidate, and not to "dress like a hippie," but signs will be available advising unaffiliated voters they can vote at the polls.

A post on Salt Lake Indivisible's Facebook page also notes that only the GOP outnumbers unaffiliated voters in Utah, and states that "many of these are disenchanted former moderate Republicans."

Unaffiliated voters must make their voices heard, it states, if "there is any hope of reclaiming Utah, and especially the very conservative 3rd Congressional District, from the clutches of the far-right contingent that overtook the party in 2010."

Glenn said that was a call to "Republicans who felt betrayed by their own party (which they feel no longer represents their true conservative values and is no longer the party of Lincoln and Reagan) to rejoin the ranks."

While the GOP no longer represents her "in any way," Glenn said members of her organization span the full spectrum of political beliefs. "It's all about ethics. That's something all good, decent people can come together on."

Judi Hilman, a co-leader of Salt Lake Indivisible, said the message to unaffiliated voters in one of the most Republican districts in the country is "if it matters to them what flavor of Republican they're getting, if they want the moderate, they can vote."

Hilman added, however, her group was "not endorsing Curtis or any of them. We're not bashing Ainge or Herrod."

Curtis, who once led the Utah County Democratic Party and ran as a Democrat but considers himself a conservative Republican, has largely been the target of close to $1 million in outside spending in the race to support Herrod and Ainge.

A newly released poll shows Curtis continues to lead in the race, although it is getting closer. Thompson said he expects to have about 10,000 to 15,000 ballots that won't be counted until a day or two after the election.

That estimate is based on an anticipated turnout below 40 percent in Utah County's first largely by-mail election and that only about 5,000 of the more than 30,000 ballots already mailed in have come from unaffiliated voters.

Utah County was already planning to count the unaffiliated ballots separately to make sure the votes are properly tabulated in the municipal races and not counted in the 3rd District primary.

Unaffiliated voters who join the GOP at the polls will be casting provisional ballots that are subject to verification. But now the county will also have to make sure any previous ballots mailed in by those new Republican voters aren't counted.

"I'm getting it from all sides, from all camps," Thompson said of the latest issue stemming from the mishap discovered after ballots were mailed out July 25.

The winner of the GOP primary will go on to face several candidates in the November general election for the remainder of Chaffetz's term, including Democrat Kathie Allen and the new United Utah Party's Jim Bennett.

Chaffetz, a Republican, was first elected in 2008 and stepped down on June 30. He is now a contributor to Fox News.