IN RECENT DAYS, BOTH MR. BIDEN AND SENATOR ELIZABETH WARREN OF MASSACHUSETTS SAID THAT MR. SANDERS SHOULD NOT BECOME THE NOMINEE IF HE ARRIVED AT THE CONVENTION SHORT OF A DELEGATE MAJORITY. “BERNIE HAD A BIG HAND IN WRITING THESE RULES,” MS. WARREN SAID DURING A CNN FORUM ON WEDNESDAY NIGHT. “I DON’T SEE HOW HE THINKS HE GETS TO CHANGE THEM NOW THAT HE THINKS THERE’S AN ADVANTAGE FOR HIM.”