Colorado Republican gubernatorial candidate Walker Stapleton is asking to intervene in a lawsuit filed last week seeking to remove U.S. Rep. Doug Lamborn from the 5th Congressional District’s GOP primary ballot – a suit that alleges some signatures on Lamborn’s petitions placing him on the ballot were gathered improperly.

Five Republican voters have sued Colorado Secretary of State Wayne Williams, alleging that several paid circulators hired by Lamborn, R-Colorado Springs, didn’t satisfy legal residency requirements.

That lawsuit, challenging a ruling by Williams that determined Lamborn qualified for the ballot, will be heard Tuesday in Denver District Court.

Lamborn filed a motion to intervene in the case late Sunday and, like Stapleton, is also asking the judge to dismiss the lawsuit.

Stapleton, the state treasurer, learned Friday that he successfully petitioned onto the June 26 primary ballot. But because hundreds of signatures on his petitions were gathered by many of the same circulators as Lamborn – both candidates hired Kennedy Enterprises, a Colorado Springs-based firm, to manage their petition drives – Stapleton is at risk of being kicked off the ballot if Lamborn loses in court.

“Mr. Stapleton has a vital interest in this lawsuit, which seeks to invalidate the genuine and verified signatures of Colorado voters gathered by the seven petition circulators identified by Petitioners and to thereby decide at least two primary elections in this courtroom rather than at the ballot box,” Stapleton’s attorneys argue in a motion filed Friday.

“Mr. Stapleton has an interest in ensuring that all signatures gathered by the named circulators in support of his candidacy are not improperly invalidated, particularly with regard to his candidacy.”

“We welcome Walker in the case,” Michael Francisco, the Colorado Springs attorney representing the Republicans suing Lamborn, told Colorado Politics in an interview. “It looks like he also used the same circulators who broke the law.”

Dan Kennedy, who runs Kennedy Enterprises, denied that his circulators did anything improper or against the law, telling Colorado Politics in an email: “[T]o the best of my knowledge, ALL of the petition circulators are Colorado residents. And ALL the signatures were gathered legally.”

In a statement issued last week, Lamborn said he was certain the lawsuit challenging his petitions lacked merit.

“This lawsuit will be dismissed soon. I have spoken to the company that gathered signatures and have been assured that all applicable laws and regulations have been followed. I look forward to continuing this spirited campaign,” he said.

For a congressional candidate, it takes 1,000 valid signatures from fellow party members to get on the ballot; for statewide candidates, including governor, it takes 10,500 – 1,500 from each of the state’s seven congressional districts.

According to the Colorado secretary of state’s office, Lamborn submitted 1,269 signatures that passed muster, while Stapleton submitted 11,325 valid signatures.

Francisco said investigators have determined that nearly 700 of Lamborn’s signatures were gathered by paid circulators who registered to vote in Colorado but “lack any real connection to Colorado” and don’t qualify as legal residents.

Using the same criteria, Francisco is alleging that more than 8,000 of Stapleton’s signatures were gathered by circulators whose claims of residency “don’t pass the smell test.”

The dispute revolves around a longstanding, routine practice employed by petition-gathering firms of hiring temporary workers, many of whom travel from state to state working petition drives.

“It’s common sense,” Francisco said in an interview. “People know these aren’t real Colorado residents. The legislature has required that, in order to circulate petitions in Colorado, you have to be a resident. These folks don’t meet these criteria. I’m disappointed people like Walker are willing to push under the rug important matters of election integrity.”

Ryan Call, a former state Republican Party chairman and one of the attorneys representing Lamborn, told Colorado Politics he expects a favorable ruling from the judge.

“The petitioners in this action are seeking to apply the wrong standard regarding the eligibility for voter registration and petition circulators, particularly in light of the changes the legislature made recently for same-day voter registration,” Call said in an interview.

“This is really, at its core, about giving the ability of the voters to decide. Procedural technicality efforts to try to disqualify candidates and supplant the process by which we pick our nominees by primary election is, in my view, not going to be successful.”