Michelle Goldberg: Elizabeth Warren is the Democrats’ unity candidate

Over the weekend, a minor conflict broke out between the presidential campaigns of Bernie Sanders and Elizabeth Warren, longtime friends who have, until now, seemed to operate under an unspoken nonaggression pact.It started when Politico reported on a script that Sanders volunteers had been given to persuade voters leaning toward other candidates. Warren backers, the script said, are “highly educated, more affluent people who are going to show up and vote Democratic no matter what” a