“Only two things are going to happen: either Bernie or brokered,” said James Carville, a veteran Democratic strategist.

Carville is uncomfortable with a Sanders nomination but fears that a brokered convention — in which party bosses or delegates in floor fights and negotiations decide the nominee after no candidate amasses enough delegates in the primary — would inflict serious damage on the party, as well. “It’s just hard for me to see beyond the two options,” he said.

South Carolina’s primary on Saturday stands as the first marker on the four-day crossroads. Joe Biden and his establishment allies hope to slow Sanders’ momentum — and change the trajectory of the race — with a convincing victory demonstrating his strength among African Americans. But just three days later, Sanders believes he’s positioned to seize a major delegate advantage when 14 states and one U.S. territory vote on “Super Tuesday.”