Joe Biden Faces the Most Dangerous Week of His Campaign So Far

Joe Biden kicks off the most high-stakes week of his campaign so far, as he heads into the first Democratic debate with the opportunity to solidify his front-runner status — or jeopardize with a gaffe, an inappropriate joke or a tone-deaf comment.

The former vice president doesn’t need to win the debate, he just needs not to lose, as his 19 rivals seek to break out of the unprecedentedly large Democratic field by taking him on. And he has given them plenty of ammunition with recent unforced errors such as...