A Kobach candidacy, while pleasing to his party’s most conservative core, would energize liberals and moderates in the two House districts up for grabs.

Paul Davis, the likely Democratic nominee in one open House district, a liberal enclave encompassing Topeka and Lawrence, said a Kobach nomination could turbocharge their turnout efforts. “For Democrats here, Kobach is seen as an even bigger lightning rod than Brownback,” Mr. Davis said.



In an interview, Mr. Colyer, the current governor, warned that nominating “Kris would bring a lot of risk” because of his unpopularity with the general electorate, citing polls that show Mr. Kobach behind the potential Democratic nominee while trumpeting his own “very broad appeal.” And, without prompting, he cited the importance of protecting the two House seats.

But Mr. Kobach argued that midterm elections are determined by which candidate can most effectively motivate the ideological base of the party, and he said that was him.

“Colyer can’t motivate anybody to turn out,” said Mr. Kobach. “That’s not his forte.”

The intraparty clash here illustrates the divisions between those Republican Party leaders who may have been more comfortable in the pre-Trump era — such as Mr. Colyer, a well-to-do and mild-mannered plastic surgeon — and those suited for the incendiary and racially-tinged politics of the moment, like the hard-charging Mr. Kobach.

But Kansas Republicans have been practicing fratricide since long before Mr. Trump descended an escalator at Trump Tower to declare his candidacy. The moderate-versus-conservative split, once rooted in a divide over abortion rights, has allowed Democrats to win the governorship over the years even as the state’s voters have sent an unbroken line of Republicans to the Senate since 1932.