Democrats have failed all year to find a cogent midterm campaign theme, but one appears to be attaching to them all the same: Listen to what we say; ignore what we do.

Nowhere is this truer than in blue, blue New Jersey, where Sen. Bob Menendez is suddenly struggling. Businessman and Republican nominee Bob Hugin has spent months educating Garden State voters on Mr. Menendez’s adventures with a now-convicted criminal. The more the voters learn, the tighter the race becomes. Recent public polls have awarded Mr. Menendez a 6- or 7-point lead, though a new internal Hugin poll claims the gap is now less than 2.

Democrats are alarmed enough that the Senate Majority PAC this week decided to reroute a precious $3 million to bolster Mr. Menendez with television advertising. The decision is extraordinary, given the number of Senate seats Democrats are already struggling to defend, many in states President Trump carried. But it is even more extraordinary for the statement—campaign theme, if you will—Democrats are rolling out with this ad buy. Namely, don’t believe us.

This is the party that claims to be running against a Republican “culture of corruption.” Democrats have highlighted the conviction of Trump campaign manager Paul Manafort and introduced anticorruption bills in Congress. House Minority Leader Nancy Pelosi in August even provided her members a “toolkit” for talking about supposed GOP misdeeds. They present the Trump White House as some mix of the yakuza and a drug cartel.

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