Democrats Wonder Whether Biden Rebound Is at Hand

A comfortable win in South Carolina would inject new life into a previously flagging campaign

WSJ's Gerald F. Seib explains how the Democratic presidential debate in Las Vegas set up a two-week stretch that may help decide who wins the nomination. Photo: Ethan Miller/Getty Images

So it appears the firewall is holding for former Vice President Joe Biden this week. If that remains the case, a key question is: How much will that matter next week?

A tense campaign week draws to a close with the South Carolina primary election Saturday. It has become almost a cliché at this point to say that South Carolina is a must-win...