When Mr. Walker, who ended his own presidential bid by offering a pointed rebuke of Mr. Trump, endorsed Mr. Cruz last Tuesday, he did so by calling in to Mr. Sykes’s show. And the week before, Mr. Cruz opened his Wisconsin primary bid in a friendly interview with Mr. Sykes.

Mr. Trump, by contrast, has found himself under near constant fire from the conservative talk radio hosts who dominate the southern part of the state, including the three counties that contain parts of Milwaukee: Waukesha, Ozaukee and Washington. They are among the most conservative counties in Wisconsin, and where Mr. Trump is struggling the most.

The most popular conservative talk show hosts here — Mr. Sykes, Jeff Wagner of WTMJ, and Mark Belling, Vicki McKenna and Jay Weber of WISN — are united in their disdain for Mr. Trump, with Jerry Bader, a radio personality at WTAQ in Green Bay, rounding out the group.

“The thing that’s been unique in this presidential race is, for some reason, the three who work here — Jay, Vicki and myself — and our competitors, Charlie and Jeff Wagner, all seem to despise Trump,” Mr. Belling said in an interview. “We all just kind of came to this conclusion independently. I think it’s just that we’re not as stupid as some of the people that are falling for Trump’s crap.”