Logan County Commissioner Jerry Sonnenberg on Friday became the fifth Republican to qualify for the GOP primary in Colorado’s 4th congressional District after election officials determined he submitted more than enough petition signatures to make the ballot.

The cattle rancher and former state lawmaker from Sterling joins U.S. Rep. Lauren Boebert, nonprofit founder and former talk radio host Deborah Flora and state Reps. Richard Holtorf of Akron and Mike Lynch of Wellington in the primary for the seat formerly held by Republican U.S. Rep. Ken Buck, who resigned in March.

Colorado congressional candidates must submit at least 1,500 valid signatures from fellow party members to qualify for the primary ballot. Of the 3,155 signatures turned in by Sonnenberg’s campaign, the Colorado Secretary of State’s Office said in a sufficiency statement that 1,719 were valid.

The already crowded primary field could get even larger next week, as three additional Republicans are awaiting review of petitions they submitted by last month’s deadline.

Some of the GOP candidates threw elbows at their rivals on Friday in statements to Colorado Politics, potentially previewing a feisty campaign for a rare open, solidly Republican seat in a state where the party has suffered historic setbacks in recent elections.

Nearly a dozen Republicans launched campaigns in the deep red district — covering Douglas County, a portion of Larimer County and the state’s Eastern Plains — after Buck announced last fall that he wouldn’t seek reelection, but the former five-term congressman from Windsor scrambled the landscape again last month when he abruptly resigned his seat. That triggered a special election to fill the remainder of his term, which which is set to occur on the same ballot as the June 25 primary.

“I continue to be humbled by the support I am receiving from voters across CD 4 — good people who I have served for two decades,” Sonnenberg said in a statement. “It is clear that CD 4 needs a proven leader who knows the needs of our district because they have deep roots here and have a demonstrated record of representing the principled, conservative values of this district with character.”

Sonnenberg then took veiled aim at Boebert, the two-term congresswoman who moved into the 4th CD from the Western Slope at the beginning of the year to run for the safer seat.

“We cannot afford to be represented by someone who seems to care more about bomb-throwing and social media stardom than serious legislating, and who shows a serious lack of judgment and personal responsibility,” Sonnenberg said.

“I am not running for Congress to become famous or get on cable news. I am running for Congress to put the needs of our district first and to represent the interests of our communities with quiet purpose. I will continue to work tirelessly to earn the support of voters across our great district that I have always loved.”

Boebert’s spokesman fired back by attempting to draw Holtorf into the squabble.

“We share Jerry’s concerns about Rep. Holtorf’s lack of judgment and personal responsibility, but we do have good news for him: based on his performance at assembly and the numbers we’ve seen, Jerry doesn’t have to worry about becoming famous any time soon,” Boebert campaign manager Drew Sexton said in a text message.

Boebert, who had already qualified for the primary by petition, won top-line designation on the ballot at last week’s district assembly in Pueblo.

At the same assembly, Sonnenberg and Holtorf fell short of the necessary 30% delegate vote to make the primary by that route alone, but both received sufficient support to still qualify by petition, which they accomplished this week. Flora and Lynch skipped the assembly and petitioned into the primary. 

Holtorf, for his part, declined on Friday to comment on Sonnenberg’s or the Boebert campaign’s remarks.

“I will not get in the middle of a quarrel between the Boebert campaign or the Sonnenberg campaign,” he said in a text message.

Flora got in a jab of her own in a statement to Colorado Politics.

“I am the only conservative in the race who can beat Congresswoman Boebert and ensure we keep the Democrats from winning a safe Republican seat by honorably serving the citizens of CD4,” Flora said in a text message.

The district’s Republicans nominated former Parker Mayor Greg Lopez to run in the special election. The two-time gubernatorial candidate, who isn’t running in the GOP’s congressional primary, faces the Democrat’s special election nominee, Trisha Calvarese, who is also seeking her party’s nomination in the primary.

Calvarese, a veteran poltiical organizer and speechwriter, faces two other Democrats in the primary: Ike McCorkle, a Marine veteran who twice ran unsuccessfully against Buck, and John Padora, an engineer and environmental scientist.

Libertarian Hannah Goodman, the minor party’s state chair, is also on the ballot for both elections.