The congressional career of six-term Republican U.S. Rep. Doug Lamborn of Colorado Springs was thrown into jeopardy after the Colorado Supreme Court ruled on Monday that he should be kept off the primary ballot in June.

While the decision — that Lamborn’s re-election campaign improperly gathered voters’ signatures to land a spot on the ticket — is unlikely to mean his 5th Congressional District seat leaves GOP hands, it injects the very real prospect that a fresh face will take over after years of unsuccessful challenges to Lamborn’s reign.

Reached by phone on Monday, Lamborn said “we’re still digesting the opinion” and then he hung up.

Contacted a second time, Lamborn said “we’re still looking at the language,” urged a reporter to contact his press secretary and then hung up again.

His campaign later issued a statement that indicated he would challenge the ruling in federal court.

Candidates can make the primary ballot in two ways in Colorado: either by gathering signatures from voters in their party or by winning the support of party insiders through a caucus and assembly process.

Lamborn took the former route, needing 1,000 signatures from registered Republicans in Colorado’s 5th Congressional District to make the ballot. He turned in 1,783 signatures to the Colorado Secretary of State’s Office, 1,269 of which were deemed valid.

Shortly thereafter, a lawsuit was filed by five Republicans from the congressman’s district challenging whether two of the signature gatherers hired by his campaign were Colorado residents as required by state law.

The Denver District Court ruled that one of the gatherers was not a resident, and invalidated 58 signatures he collected. It found that the other — who had gathered more 269 signatures — was.

But the Colorado Supreme Court, which reviewed the case upon appeal, rejected the lower court’s ruling on the residency of the second gatherer, Ryan Tipple, which was based off the legal theory that he intended to move to the state.

“Tipple’s stated intent to live in Colorado in the future is relevant only if he has a fixed habitation in Colorado to which he presently intends to return,” the Supreme Court’s ruling said. “The record reveals none. … All of the objective record evidence regarding his residency at the time he circulated the petition for the Lamborn Campaign indicated that his primary place of abode was in California.”

The ruling left Lamborn 58 signatures short of 1,000.

The court added: “We recognize the gravity of this conclusion, but Colorado law does not permit us to conclude otherwise.”

Lamborn can no longer seek to validate other signatures that were initially rejected by Colorado Secretary of State’s Office as his deadline to do so has passed, according to agency officials.

But they acknowledged Lamborn could appeal the ruling in federal court and try to have the residency requirement for petition circulators changed to that of what’s mandated for ballot initiative signature gatherers, who aren’t required to live in Colorado.

“The Colorado Supreme Court just provided an avenue to have a federal court strike down residency requirements for candidate circulators,” Deputy Colorado Secretary of State Suzanne Staiert said in a statement.

Lamborn’s district is heavily Republican, and he won reelection in 2016 by a 32-point margin over his Democratic challenger. Two notable Republicans are challenging him for the seat: state Sen. Owen Hill and El Paso County Commissioner Darryl Glenn.

Glenn didn’t offer a prediction Monday on the congressman’s fate — though he conceded “the court could have essentially ended things for him today.”

“My wife and I will be praying for Doug and his family,” he said. “Politics is tough.”

Colorado’s secretary of state announced in February that Glenn had successfully petitioned onto the ballot with more than 1,239 accepted signatures. Hill made the ballot through the assembly process last month.

Lamborn, who is a strong anti-abortion voice in Congress, was first elected to the U.S. House in 2006 after serving as a Colorado state lawmaker. He is a member of the House Armed Services and Natural Resources committees.