photo by: John Hanna, Associated Press

U.S. Rep. Roger Marshall, left, R-Kan., shakes hands with former Kansas Gov. Jeff Colyer after receiving Colyer's endorsement in the U.S. Senate race on Monday, Feb. 24, 2020, in Topeka. Colyer is urging Republicans to unite behind Marshall as he battles former Kansas Secretary of State Kris Kobach for the GOP nomination.

Updated at 12:25 p.m. Monday

TOPEKA — Former GOP Gov. Jeff Colyer on Monday endorsed western Kansas Rep. Roger Marshall for the state’s open U.S. Senate seat with some Republicans still fearing a repeat of Colyer’s narrow primary loss in 2018 to polarizing conservative Kris Kobach.

Marshall said before a Monday news conference in Topeka with Colyer that the race for the Republican nomination in the August primary is essentially a contest between him and Kobach, the former Kansas secretary of state.

“You’re starting to see a consolidation of people behind Roger Marshall,” Colyer told reporters.

Kobach defeated Colyer by 343 votes in a seven-candidate primary for governor in 2018 and lost the general election to Democrat Laura Kelly. Marshall and other Republicans argue that Colyer would have prevailed in a one-on-one race with Kobach and won the general election.

Some GOP leaders fear a Kobach victory in the Senate primary could put a normally safe seat in play.

Kobach contends he would fare better with President Donald Trump on the ballot. But he has alienated many GOP moderates after two decades of advocating tough immigration policies.

Marshall, a two-term congressman, also has been endorsed by Kansas political icon and 1996 GOP presidential nominee Bob Dole.

Other GOP Senate candidates include Kansas Senate President Susan Wagle, of Wichita, and Dave Lindstrom, a Kansas City-area businessman and former Kansas City Chiefs professional football player.

“They’re good people, but I think that they would play the role of spoiler,” Marshall said before his news conference.