THE BURNED OVER DISTRICT

Is not happy with the Republican Tax Disaster and is letting everybody know it. The reason is quite obvious, the family business that keeps Sen. Ron Johnson of Wisconsin fat and sassy is not getting the proper tax break that larger corporations are getting.

Mr. Johnson had become the first Senate Republican to say publicly that he could not vote for the Senate’s version of the tax bill. During the phone call on Wednesday afternoon, Mr. Ryan, who had campaigned heavily for Mr. Johnson in 2016, posed an essential question, according to the senator: “What are you going to need?”

What Mr. Johnson needs, he said in an interview from Wisconsin on Friday, is for the bill to treat more favorably small businesses and other so-called pass-through entities — businesses whose profits are distributed to their owners and taxed at rates for individuals. Such entities, including Mr. Johnson’s family-run plastics manufacturing business, account for more than half of the nation’s business income, and the senator says the tax bill would give an unfair advantage to larger corporations.

“I just have in my heart a real affinity for these owner-operated pass-throughs,” he said. “We need to make American businesses competitive — they’re not right now. But in making businesses competitive, we can’t leave behind the pass-throughs.”

The sudden fissure between longtime allies laid bare the challenge that Republicans face as the tax bill leaves Mr. Ryan’s care and navigates the rough waters of the Senate, where different priorities within the party could sink the bill if not adequately addressed.

Senate Republican leaders, who are seeking a major legislative victory before year’s end, hope to bring their tax bill, which differs significantly from the House measure, to a vote after Thanksgiving. But it is unclear whether it has enough support to pass in the narrowly divided chamber.

Offering concessions to skeptical senators one by one could prove an impossible task for Republican leaders, who face restraints under Senate rules on the total size of the tax cut package. Those leaders are hoping, instead, that they can pull off a version of Mr. Ryan’s strategy: all but daring holdouts to derail the party’s top priority.

Republicans, who control Congress and the White House, are desperately seeking their first significant legislative achievement of the Trump presidency. Mr. Johnson’s public wavering elicited calls from President Trump and a visit from Treasury Secretary Steven Mnuchin and Gary D. Cohn, chairman of the National Economic Council, all of whom sounded out Mr. Johnson about his concerns.

Mr. Johnson is a firm believer in the power of tax cuts to lift economic growth. He grew up on a Minnesota farm, worked as an accountant after college, and spent more than 30 years immersed in his family’s plastics company before assuming his Senate seat in 2010.

In an election year with a real chance that Ron will be thrown out, he is not going to vote for somthing that will break his rice bowl when he is sent back home. And if the Senate makes changes to keep him happy, they may not have the offsets to keep the bill within reconciliation limits. And Ron is only the first to ask for his special interest.