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 of those nominees eventually ascended to the high court bench.

“The single most important explanation for rejections of Supreme...