Owen Hill, a Republican challenging U.S. Rep. Doug Lamborn, wants to oppose Lamborn in federal court in a case that could keep the six-term incumbent off the June primary ballot.

Hill, a Colorado Springs state senator and one of four Republicans trying to unseat Lamborn, plans to file a motion to intervene in the U.S. District Court lawsuit Lamborn’s attorneys filed Wednesday that aims to overturn a state law the Colorado Supreme Court said this week should disqualify Lamborn from the primary.

“Now that Doug is trying to use an activist court to overturn long-standing state laws, as a lawmaker and a candidate I will do everything I can to fight for the integrity of the election process,” Hill told Colorado Politics.

At issue is a Colorado law that says only state residents can collect signatures for candidates petitioning onto the ballot. The state’s high court ruled Monday that one of the petition circulators hired by Lamborn didn’t meet residency requirements, which left Lamborn without enough signatures to qualify for the primary.

While Lamborn can’t appeal that ruling, he is asking a federal court to declare the residency requirement unconstitutional.

Former Secretary of State Scott Gessler, an election law attorney, will be representing Hill in the lawsuit, a Hill campaign spokesman said.

A spokesman for the group of El Paso County Republicans who first sued to keep Lamborn off the ballot said those voters plan to join a number of state lawmakers led by state Rep. Dave Williams, a Colorado Springs Republican, opposing Lamborn in federal court.

“This case raises the real interest of protecting the rights of party association in partisan primary elections,” Kyle Fisk said in a statement.

Williams said in a statement that the lawmakers “have an obligation to protect our state’s interest from interference on the federal level.”

He added: “These petition circulator requirements are not only constitutional, they are common sense protections against election fraud. We will strongly ask the Court for a seat at the table in this case to ensure most vigorous defense possible of our state law and state interests.”

Fisk said Lamborn’s attorneys have pledged not to oppose their motion to intervene and noted that Gessler will be working with Michael Francisco, the attorney who filed the first lawsuit that forced Lamborn from the ballot.

Lamborn and his allies have charged all along that Hill was behind the original lawsuit, something Hill and Francisco denied.

Francisco and Michael Kuhn, one of the Republican voters who filed the lawsuit in state court, have both donated to Hill’s congressional campaign – but so has Ryan Call, the attorney representing Lamborn’s campaign, they point out.

“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 told Colorado Politics in an earlier 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 was the only Republican in the race to get on the ballot through the 5th Congressional District’s GOP assembly, where he was nominated by acclamation.

Glenn, an El Paso County commissioner, is one of the other Republicans running for Lamborn’s seat. He told Colorado Politics on Wednesday that he was aware of the federal case but “will not be participating” in it.

The other El Paso County Republicans who sued Lamborn are Ashlee Springer, Lydia K. Honken, Jeremy Isaac and Sharon M. Schafer.

Lamborn, first elected to Congress in 2006 after serving a dozen years in the state legislature, has faced primary opponents in all but one of his bids for reelection.