Brett Kavanaugh’s confirmation once seemed like a slam dunk. Now, it’s no longer a sure thing as the Senate investigates Christine Blasey Ford’s allegations of sexual assault during a high school party in the 1980s.

It’s not clear what will happen with Kavanaugh, but failed Supreme Court nominations aren’t all that rare.

Thirty-seven percent of nominations submitted to the Senate for confirmation have been foiled for one reason or another, according to statistics provided by the U.S. Senate. Still, many...