When Hillary steals the nomination from Obama at the convention, what will his supporters do?

It's clear that Hillary cannot get the nomination through the established primary/caucus system. Obama's lead, though small, is insurmountable. So, Hillary will steal the nomination by pressuring superdelegates and by seating the Florida and Michigan delegates elected in their primaries. When this happens (and it certainly will because the Clintons will not be denied the nomination), what will the millions of loyal Obama supporters do?