TRENTON -- Half of New Jersey's voters say Robert Menendez, the state's Democratic U.S. senator standing trial on federal corruption charges, should not be re-elected next year, according to a new poll.

The Quinnipiac University Poll released Thursday found 50 percent of voters say Menendez does not deserve to win a fourth term, while 20 percent say he does and 30 percent are undecided.

Meanwhile, 31 percent of voters approve of Menendez's job performance, while 49 percent disapprove -- the senator's lowest rating since February 2008.

Menendez fairs better among his own party. Forty-five percent of Democrats approve of his performance, while 35 percent disapprove.

The numbers are a notable drop from a Quinnipiac Poll from June, months before Menendez's trial started Sept. 6.

That survey howed 44 percent of Jersey voters said Menendez does not deserve re-election, while 31 percent said he does. That poll also found 44 percent approved of Menendez's job performance, while 35 percent disapproved.

Maurice Carroll, the poll's assistant director, said Thursday's poll numbers suggest the trial is "perhaps poisoning the landscape."

"If Sen. Menendez is convicted, he obviously won't be in the running next year," Carroll added. "If he is acquitted, who knows."

Menendez's ratings are still higher than Gov. Chris Christie and President Donald Trump in New Jersey.

Christie's approval rating among the state's voters is at a historic low of 16 percent -- 1 percentage point higher than Quinnipiac's June poll. Trump's mark is at 32 percent -- 6 percentage points higher than the June survey.

Both Christie and Trump are Republicans. Registered Democrats outnumber registered Republican by nearly 2-to-1 in New Jersey.

The state's other U.S. senator, Democrat Cory Booker, has an approval rating of 55 percent -- a drop of 3 percentage points from June.

Menendez is accused of using his office to do favors for a friend and receive gifts in return. The senator has maintained his innocence.

If Menendez is convicted or resigns, New Jersey's governor is tasked with picking a replacement to fill the senator's seat.

Who will be governor at that point depends. Christie leaves office in January, and voters pick his successor in the Nov. 7 election. Democrat Phil Murphy, a former U.S. ambassador to Germany, is leading Republican Kim Guadagno, Christie's lieutenant governor, by double digits in all polls.

It appears Menendez's trial could stretch on through the end of November, after the election. Christie could choose a successor if Menendez steps down before January, or he could allow the winner of the election to choose.

Christie or Guadagno would likely pick a Republican at a time when the GOP holds a thin 52-seat majority in the 100-seat Senate. Murphy would likely pick a Democrat.

Thursday's Quinnipiac poll found 68 percent of voters say Christie should let the next governor fill Menendez's seat, while 24 percent say Christie should fill it.

Three percent said Christie should appoint himself to the seat -- which Christie himself has said is unlikely.

The poll was conducted via phone from Sept. 7-12 with 1,121 registered New Jersey voters. The margin of error was plus-or-minus 4 percentage points.

Brent Johnson may be reached at bjohnson@njadvancemedia.com. Follow him on Twitter @johnsb01. Find NJ.com Politics on Facebook.