For years, a coalition of well-funded groups on the religious right have waged an uphill battle to repeal a 1954 law that bans churches and other nonprofit groups from engaging in political activity. Now, those groups are edging toward a once-improbable victory as Republican lawmakers, with the enthusiastic backing of President Trump, prepare to  rewrite large swaths of the United States tax code as part of the $1.5 trillion tax package moving through Congress.