DENVER — An attorney representing U.S. Rep. Doug Lamborn made a last-ditch argument Monday that a federal judge should place the six-term congressman back on the GOP primary ballot, contending the Colorado law that led the state supreme court to boot him off the ticket last week was unconstitutional.

The Colorado Supreme Court ruled that one of the people who collected the requisite 1,000 signatures of registered Republicans for the Lamborn campaign lived out of state, and that the signatures he gathered should be removed from the congressman's total.

Attorney Ryan Call noted that multiple federal appellate courts, including the 10th Circuit in Denver, have found that residency requirements for signature gatherers violate the U.S. Constitution's First Amendment.

He urged U.S. District Court Judge Philip. A. Brimmer to issue an injunction ordering Lamborn's name be placed on the ballot, which will be finalized Wednesday.

"If this court decides not to proceed with the preliminary injunction, it will significantly alter the calculus of campaigns," said Call, noting that rivals may step up challenges over residency.

The lawsuit that knocked Lamborn off the Republican primary ballot was filed by supporters of one of his primary challengers, State Sen Owen Hill. Former El Paso County Commissioner Daryl Glen is also on the June 26 primary ballot for the seat representing the Colorado Springs-area district.

Matthew Grove of the Colorado Attorney General's office acknowledged that the Colorado law requiring petition gatherers to live in the state may be questionable on constitutional grounds. But he contended Lamborn waited too late to file the lawsuit.

"If there's concern about the petition circulator residency requirement, there's been years, decades," for a challenge, said Grove, noting that Lamborn only had to collect 1,000 signatures in a district with 200,000 registered Republican voters.

Brimmer said he would issue a written ruling later.

Lamborn has also filed a lawsuit in Denver District Court challenging the Colorado Secretary of State for disqualifying several hundred signatures for technical reasons.

Lamborn's campaign initially gathered 1783 signatures, but the secretary of state's office removed 514 of those in its routine review of errors or technical violations. That left him with more than 1269 valid signatures when the lawsuit challenging his petition circulators' residence was filed.

The trial court struck 58 of the remaining signatures. When the supreme court removed another 269, that brought Lamborn to 942 signatures and just short of the ballot threshold.

If Lamborn can successfully restore some of the signatures removed by the secretary of state's office he could get back on the ballot. Otherwise, his only option would be to mount a write-in candidacy if he fails to win the injunction placing his name on the ballot that he was seeking Monday in federal court.