State Sen. Stanley Rosenberg, for decades one of the most powerful Democrats in Massachusetts, announced Thursday that he will resign Friday after 31 years as a lawmaker because of a scandal involving his estranged husband. His decision follows Wednesday’s release of an ethics report that states Rosenberg “failed to protect the Senate” from his estranged husband, who faces charges of racially and sexually harassing Senate employees. Rosenberg, 68, of Amherst, a former president of the Massachusetts Senate, was the first openly gay lawmaker to lead a legislative chamber in the Bay State, Boston’s Fox 25 reported. He stepped down as...