As Senate Majority Leader Chuck Schumer moves closer to a vote that would put Sen. Ron Johnson on defense in the home stretch of the midterms, the Wisconsin conservative is suddenly under the microscope on a social issue that he’s rarely focused on during his decade-plus in office. But it’s far from clear whether he’ll take that baby step to the center ahead of a November contest against Democratic Lt. Gov. Mandela Barnes, who’s opened a slight lead in public polls.

Johnson surprised many fellow senators last month when he said he saw “no reason” to oppose what he described as unnecessary House-passed legislation designed to protect same-sex marriage, which could come to the floor as soon as next month. Then, when pressed later, he hedged on whether he’d vote yes or merely present. And he’s now pushing, alongside other Senate Republicans, for the bill to be amended before declaring his support…

Taking up same-sex marriage legislation in September would give Democrats a plum opportunity to squeeze Johnson on an issue that more than 70 percent of Americans support, weeks before he faces off against Barnes. Even so, Johnson’s Democratic home-state colleague, Sen. Tammy Baldwin — who’s leading the effort to get the 10 Republican votes necessary to avoid a filibuster — isn’t counting on him to bring it home.

“We feel confident we will have the Republican support we need with or without Johnson,” said a Baldwin spokesperson.