They point out that Mr. Menendez is saddled with high unfavorability ratings caused by ethics troubles; his Senate duties have kept him in Washington for days at a time; and his wealthy Republican opponent, Bob Hugin, has spent millions of dollars hammering Mr. Menendez with negative ads.

Two recent polls had the two men essentially in a statistical dead heat. Two others offered better news for Mr. Menendez, giving him a slight double-digit lead, but the consistently negative views of the senator have not comforted state party leaders…

But perhaps in a small sign that national leaders were heeding the worries of local Democrats, the Senate’s campaign committee recently set aside $400,000 for coordinated advertising in the race, still a modest sum given that New Jersey sits between New York and Philadelphia, two of the country’s largest and most expensive television markets.