In an earlier time, it might have been pistols at 20 paces. On Wednesday, however, former U.S. Rep. Tom Tancredo challenged Mike Coffman, the Republican who succeeded him in Congress, to run against him for governor of Colorado in next year’s GOP primary.

“Run against me – absolutely, I’m all for it, buddy,” Tancredo taunted on Peter Boyles’ morning show on 710KNUS.

“I think this would be more fun than anything,” he added.

Tancredo was upping the ante on a gauntlet Coffman threw down in an interview with 9News Monday, when Coffman invited Tancredo to challenge him in a primary for the 6th Congressional District seat.

“We could define what the Republican party is for a generation to come,” said Coffman.

“I’ve got a better idea,” Tancredo said in his radio appearance. “I think we can accomplish that goal – it sounds great to me – and do it in a way that really would be far more effective. Instead of running in a 6th Congressional District race – by the way, in which I don’t live, though you could still do it – let’s do this, Mike. Let’s you and I run against each other in the Republican primary for governor. Let’s do that statewide, and then that would definitely become a national campaign.”

Tancredo, who represented the congressional seat for five terms and has run for governor twice since leaving office, has been exploring a run for governor in 2018, when incumbent Democrat John Hickenlooper faces term limits.

A Coffman campaign spokesman scoffed at Tancredo’s suggestion.

“Mike’s won literally the toughest races in America cycle after cycle,” said Kyle Kohli, in a statement. “Tom is a former safe-seat congressman whose claim to fame is a broken term limits pledge and a deciding vote for the trillion dollar bank bailout. Tom knows Mike isn’t running for governor, just as Tom probably isn’t going back to running the national term limits movement.”

The two Republicans have been sparring for weeks over immigration policy.

Tancredo, who ran for president in 2008 to bring a hard-line immigration stance to the national stage, has criticized Coffman for his recent positions on undocumented immigrants brought to the United States as children. Known as Dreamers, their plight has taken center stage since President Trump announced earlier this month he was canceling an Obama program that offered legal status. Coffman has signed on to a Democratic proposal that would resurrect protection for the immigrants and establish a path to citizenship.

Trancredo has been calling for a conservative candidate to challenge Coffman in next year’s congressional primary in the swing district. (Since Tancredo won election there five times, it’s been redrawn from a heavily Republican seat to one nearly evenly split between Republicans, Democrats and unaffiliated voters, and also now has a sizable Hispanic and immigrant population.)

Coffman, for his part, has been swinging back at Tancredo, charging his predecessor with supporting VDARE, a group Coffman called a “white supremacist organization.” (Tancredo said he was motivated to consider a run for governor by his anger at Republicans for staying silent when a Colorado Springs resort canceled a VDARE conference.)

“He’s going to have one of his friends do that, one of his white supremacist friends, try and run against me, ” Coffman told 9News reporter Brandon Rittiman. “Why not him?”

The two also traded barbs recently about Tancredo’s motivation for a possible gubernatorial run. Coffman mused on a radio appearance that Tancredo was bored and missed the spotlight, while Tancredo shot back at a recent tea party meeting that he was concerned about the direction leading Colorado Republicans appeared to be taking the party.

If Coffman takes Tancredo up on his challenge, it could push the GOP gubernatorial primary field into double digits. Already, seven Republicans are in the race, with another three who’ve said they’re considering a run, including Coffman’s soon-to-be-ex wife, Attorney General Cynthia Coffman.

This story has been updated to include a comment from the Coffman campaign.