New Jersey Sen. Robert Menendez is in the legal fight of his life. And if he runs for re-election in 2018, he may be in for his toughest political fight, too. 

Half of New Jersey voters said the state’s senior Democratic senator does not deserve to be re-elected next year, according to a Quinnipiac Poll released Thursday.

Only 20 percent said he deserves to be re-elected. Thirty percent said they didn’t know.

Menendez, who’s on trial for federal corruption, suffered from low approval ratings in the poll. Thirty-one percent of voters said they approve of the way he’s handling his job, while 49 percent said they disapproved. 

Menendez is on trial for allegedly receiving bribes from Florida ophthalmologist Salomon Melgen in exchange for using his office to benefit Melgen. The trial, which is expected to last about two months, is in its second week in Newark.

Republicans are hoping that if the senator is convicted this year and resigns, GOP Gov. Chris Christie would have an opportunity to appoint a Republican replacement before his gubernatorial term is over. 

Quinnipiac asked voters how the senator should be replaced if he is “forced to leave” the Senate. Only 3 percent said they’d like Christie to appoint himself to the seat. Christie’s job approval rating is 16 percent in the same poll.

About a quarter of voters said they’d want the governor to appoint someone else to the seat. But an overwhelmingly majority (68 percent) said they’d want Christie to wait for the new governor to make the appointment. 

The gubernatorial election is Nov. 7, with the new governor likely to be sworn in early next year. Democrat Phil Murphy led Republican Lt. Gov. Kim Guadagno 58 to 33 percent among likely voters in a Quinnipiac Poll released Wednesday. 

For Thursday’s poll, Quinnipiac conducted live interviews with 1,121 registered voters on landlines and cell phones between Sept. 7 -12. The margin of error was plus or minus 4.4 percent. 

Menendez, who was first elected to the House in 1992, won election to the Senate by 9 points in 2006. He won re-election by nearly 20 points in 2012. Inside Elections with Nathan L. Gonzales rates the Senate race Solid Democratic.