Sen. Ron Johnson has gone from tea party insurgent to a top Trump cheerleader in 2022, and Wisconsin voters will decide this year whether they are on board with his political evolution. Mr. Johnson, a businessman who won his seat in the 2010 GOP wave election, is one of the Democrats’ top targets this year. They hope voters have tired of Mr. Johnson and his refusal to embrace Washington norms, his outspoken complaints about crumbling borders, his support for overturning Roe v. Wade and his allegiance to former President Donald Trump. And yet, it was Mr. Johnson’s maverick streak that...