New Jersey voters have sadly become all too familiar with politicians getting indicted on corruption charges. But that doesn’t mean they’ve entirely lost their sense of outrage over Sen. Bob Menendez, the incumbent Democrat who has been seeking re-election while pretending that a hung jury represents vindication. Now his campaign has a problem beyond his ethical challenges.

When a Monday Stockton University survey showed that Republican challenger Bob Hugin had pulled within the margin of error against Mr. Menendez, left-leaning...