“The only chance of holding the seat is with John. And when he leaves, we probably lose the seat,” said Steve Wells, a Katko donor and fundraiser.

“I’m a conservative, but I’m also pragmatic,” said Gary Lavine, an attorney in Syracuse who has been active in Republican politics for more than 50 years. “We will have a Democrat for the foreseeable future in the Syracuse-Ithaca district unless Katko runs and wins, and I predict he will run and he will win.”

“Is he conservative? Is he liberal?” Fitzpatrick, the Onondaga DA, said of Katko. “He’s conscientious. He votes the way he thinks is right.”

“There’s a level of independence there that I think is attractive to a moderate district,” said McMahon, the Republican county executive. “And it drives the far right and the far left nuts.”