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A conservative watchdog group is calling on Nevada officials to intervene to ensure SEIU workers who operate one county's voting machines don't skew the results to boost their endorsed candidate, Senate Majority Leader Harry Reid.

A contract between SEIU Local 1107 and Clark County -- where voting glitches were reported Tuesday -- makes the SEIU the sole union representative for, among other professions, voting machine technicians.

Nevada SEIU spokesman Nick Di Archangel called the suggestion that SEIU or its technicians would manipulate voting machines "absolutely false."

But Americans for Limited Government called the union agreement "positively outrageous" considering SEIU's political stake in the race. ALG has urged the U.S. Marshals, the state attorney general and the U.S. attorney's office to step in to uphold the integrity of the election.

"For all intents and purposes, the SEIU has control over those ballots boxes, because they're the people who work on them ... which puts us into a new realm of potential fraud," ALG spokesman Richard Manning told FoxNews.com.

Manning said it is "suspicious" that glitches were just reported in that county's machines, referring to complaints from voters in Boulder City that Reid's name was already checked when they went to cast their ballots for his opponent, Republican Sharron Angle. Fox5Vegas.com reported that several voters in the Clark County jurisdiction experienced the same problem.

Registrar of Voters Larry Lomax explained that highly sensitive touch-screens may be to blame and fraud is not the issue. He told Fox5Vegas.com that nobody reported the problem to his officials and that it would be impossible for the machines to pick a candidate without the voter's consent.

He also said in a statement that the supervisors are not part of the union, even if the technicians are, and that the technicians are not involved in programming. He said "extensive security measures are in place" to prevent tampering, adding that SEIU-eligible employees have worked in the Election Department for years without incident.

Di Archangel said Lomax "ensures both the security and reliability" of the machines. "The machines cannot be compromised," he said in an e-mail to FoxNews.com. He added that despite the county contract, all workers are free to stay out of the union if they wish.

"The agreement does not mandate in any way that only union members be assigned to specific jobs," he said.

Secretary of State Ross Miller's office said in a statement that despite wide-ranging "rumor and speculation" about suspicious voting activity, no formal complaints have been lodged with Nevada's Election Integrity Task Force.

"I will not tolerate any attempt by an individual, organization or campaign, to deny any Nevadan the right to freely cast their vote in a safe, secure and private manner. But neither will I stand by and allow the public's confidence in the electoral system (to) be undermined by unsubstantiated rumors and allegations," Miller said.

But Manning said SEIU's involvement in the process raises concern about the integrity of the election.

The union is putting big money into the Nevada Senate race to support Reid and recently went up with an ad that described Angle as "too dangerous" to have power in Congress.

Though the Clark County/SEIU contract is dated March 2007 to June 2010, it is still in effect.

The SEIU said that voters, to ensure the accuracy of their selections, should use the machines' "fail-safe system" to review their picks before leaving the polling station.