The senior Republican in Maricopa County, Jack Sellers, the chairman of the board of supervisors, said flatly that the county would stop cooperating with the review and suggested that it would challenge in court any of its conclusions that pointed toward improprieties. “This board is done explaining anything,” Mr. Sellers said at a special meeting of the five-member board, four of whose members are Republicans. “People’s ballots and money are not make-believe. It’s time to be done with this craziness, and get on with this county’s critical business.”... “This board was going to be part of a political theater,” one Republican supervisor and former chairman of the board, Bill Gates, said. “The Arizona Senate is better than that. The Maricopa County Board of Supervisors is better than that. And I am not going to be a part of that.” Mr. Trump had seized on the deleted-file claim over the weekend, calling it “devastating” evidence of irregularities in the vote. That led the county’s top election official, Stephen Richer, to call Mr. Trump’s online comment “unhinged.”