DENVER – A lawsuit filed Tuesday by five Republican voters is asking a judge to remove U.S. Rep. Doug Lamborn from the 5th Congressional District’s GOP primary ballot, alleging petition circulators hired by Lamborn didn’t meet legal requirements to gather signatures for his campaign.

The lawsuit, filed in Denver District Court, claims Lamborn fell more than 400 signatures short of the 1,000 needed to qualify for the June primary. Colorado Secretary of State Wayne Williams said last week that Lamborn had submitted 1,269 valid signatures.

“Shockingly, the overwhelming majority of these signatures were gathered by the illegal use of paid out-of-state circulators who fail to meet the Colorado legal requirement that circulators be properly registered to vote as Republican, with legal residence in Colorado,” the lawsuit reads.

Michael Francisco, the Colorado Springs attorney representing the plaintiffs, told Colorado Politics that his firm’s investigator determined that nearly 700 of Lamborn’s signatures were gathered by seven circulators, many from Michigan, who registered to vote in late January at a house in Thornton but “lack any real connection to Colorado.”

It’s been a longstanding practice for petition-gathering firms to hire temporary workers, many of whom travel from state to state working petition drives. But Francisco said that merely claiming an address in Colorado doesn’t meet the state’s requirements for residency, such as having a Colorado driver’s license, registering a vehicle in the state, or owning property, including household items.

“The math here is staggering – over half of his signatures come from these seven people who every indication shows are not residents and should never have been registered as Republicans here in Colorado,” Francisco said in an interview. “Everybody knows you have to follow the rules.”

In a statement, Lamborn’s campaign dismissed the lawsuit’s argument.

“The campaign for Lamborn for Congress stands by the determination of the Secretary of State’s office that the signatures are sufficient,” a campaign spokesperson who refused to give his or her name wrote in a text message to Colorado Politics.

Lamborn is facing four Republican primary challengers, including two others who have already made the ballot and two whose petitions are under review by Williams’ office. El Paso County Commissioner Darryl Glenn qualified for the ballot by petition in late February, and state Sen. Owen Hill, R-Colorado Springs, won a spot at the Republican district assembly on Saturday. Retired Texas state judge Bill Rhea and former Green Mountain Falls Mayor Tyler Stevens have submitted petitions.

“I believe in the rule of law,” said Michael Kuhn, one of the 5th District Republicans who filed the lawsuit. “Elections should be fair, and all of our candidates should play by the rules, including candidates who bypass the assembly process and seek to petition onto the ballot.”

The other Republicans suing Lamborn are Ashlee Springer, Lydia K. Honken, Jeremy Isaac and Sharon M. Schafer.

Francisco and Kuhn have both donated to Hill’s congressional campaign, but Francisco said the lawsuit was “absolutely not on behalf of any candidate” and instead was aimed at Lamborn because the six-term incumbent skipped the assembly process by petitioning onto the ballot.

“A number of the plaintiffs were not pleased that Doug Lamborn offended everybody who bothered to show up, going to caucus and going to assembly,” Francisco said in an interview. “Personally, in various races, I’ve supported Darryl Glenn, Doug Lamborn and Owen Hill over the years. But Doug Lamborn stuck his thumb in the nose of everyone who was a Republican who went through the assembly process – and he broke the law.”

Hill said in a statement to Colorado Politics that his campaign wasn’t involved in the lawsuit, but he didn’t disagree with its goals.

“I know I speak for all Colorado voters when I say that the integrity of our election process is paramount,” Hill said. “I’ve not talked with any of the petitioners or their lawyer about the lawsuit against Doug Lamborn, but I’m personally grateful to have earned the support of grassroots Republicans at the District assembly this past Saturday and have my name on the top of the primary ballot without controversy.”

Glenn declined to comment, citing a policy against weighing in on pending litigation.

Dan Kennedy, head of Colorado Springs-based Kennedy Enterprises, a firm hired by the Lamborn campaign to gather petition signatures, told Colorado Politics in an email that he’d heard about the lawsuit on a talk radio show Wednesday morning. “And to the best of my knowledge, ALL of the petition circulators are Colorado residents. And ALL the signatures were gathered legally,” Kennedy wrote.

Ben Schler, the legal policy manager for the secretary of state, said election officials had done “exactly what we’re supposed to do,” verifying on voter registration records that petition circulators are affiliated with the party of the candidate whose petition they’re circulating.

“We did our job, but anybody is entitled to that challenge under the statute where you can go to the court and say, ‘We think there’s an issue there,'” Schler said in an interview. “The court, unlike the secretary of state, can hear evidence on a case that’s going to be very factually based. That is the proper place to take it.”

He maintained that the questions raised in the lawsuit are beyond the scope of the secretary of state’s petition review process.

“For us to conduct investigations into something like residence and things like that, that’s a pretty slippery slope, and not only for petitions but voter registration in general,” Schler said. He added, “We are not in the business of saying, ‘OK, this person has only been registered for three weeks or for the duration of the circulation, let’s give them a call and ask them if this is their residence.'”