State Sen. Owen Hill, one of four Republicans challenging U.S. Rep. Doug Lamborn, has dropped plans to circulate petitions and will put all his chips on the 5th Congressional District assembly to make the June primary ballot, the Colorado Springs lawmaker told Colorado Politics.

A campaign spokesman for Lamborn, who turned in petitions to the secretary of state’s office earlier this week, said the six-term GOP congressman is weighing his options and might also try to qualify for the ballot through assembly, which requires winning the support of at least 30 percent of delegates.

“Lamborn for Congress turned in roughly 1,800 signatures. The congressman continues to keep all options open,” Dean Miller, the campaign’s press secretary, told Colorado Politics in an email.

The Republican congressional district assembly is scheduled for March 31 in Colorado Springs.

“We’re working relentlessly to earn the support of our neighbors and have no intention of buying our way onto the ballot,” Hill said in a statement to Colorado Politics. “With my strong record of results, I look forward to dueling Doug at the assembly and earning the overwhelming support of Republican voters on March 31.”

Both candidates said in January that they were considering going through assembly in addition to or instead of petitioning on the ballot.

In order to qualify by petition, congressional candidates have to turn in 1,000 signatures from fellow party members who live in their district. This year, under a new procedure, the secretary of state’s office is determining whether voters’ signatures match the ones on file, in addition to verifying that all the other information matches voter records.

Another one of Lamborn’s challengers, El Paso County Commissioner Darryl Glenn, learned at the end of February that he’ll be on the June 26 primary ballot when state officials declared he had submitted enough valid signatures on his petition earlier in the month. So far, Glenn is the only candidate in the state whose petition has been declared sufficient, although several other candidates’ petitions are under review.

Two other Republicans running against Lamborn – former Texas state judge Bill Rhea and former Green Mountain Falls Mayor Tyler Stevens – are chasing signatures in hopes of making the ballot.

The deadline to turn in petitions is March 20. Candidates could start gathering signatures on Jan. 16.

Two years ago, Lamborn nearly lost the nomination outright at the congressional assembly, when activist Calandra Vargas held the incumbent to 35 percent – just 18 votes more than he needed to advance to the primary, which Lamborn won with 68 percent of the vote.

Lamborn skipped the assembly and made the ballot by petition in 2008, when he was facing two GOP challengers in his first run for reelection. At the time, Lamborn said said he wasn’t confident the El Paso County GOP could handle the assembly fairly.

Four Democrats – including three who are circulating petitions – are also running in the heavily Republican district, which covers El Paso, Chaffee, Freemont and Teller counties and portions of Park County.