1. The “Front-Runners.

In the Iowa caucuses, former Vice President Joe Biden got 15% of the “first vote.” In New Hampshire eight days later, he got 8.4% of the primary vote. In the Nevada caucuses, 11 days after that, he got 20% of the “first alignment votes.” Last night in South Carolina. Mr. Biden got 48.4% of the vote, winning every county and beating the party’s putative front-runner, Sen. Bernie Sanders, by a margin of nearly two-and-a-half to one. Had Biden not done so, and as convincingly as he did, he probably would have had to end his campaign.