TRENTON -- A new poll has a new theory to help explain why Republican nominee Kim Guadagno has been struggling in the New Jersey's governor's race:

Many Republican voters in the state appear to have left the party because of President Donald Trump.

The analysis by the Fairleigh Dickinson University Public Mind Poll, released Wednesday, found 14 percent of registered Republicans who are likely to vote now say they're Democrats. By contrast, 6 percent of registered Democrats now say they're Republicans.

Dan Cassino, a political science professor at FDU and an analyst for the poll, said it's common for voters to "move between being independent and partisan," but it "much rarer to see this many people" moving between parties.

The poll said voters might shift parties for various reasons, but the fact both parties have become more uniform in their views of Trump, a Republican, indicate he's the main force behind the change.

And Cassino said this puts Guadagno, the state's lieutenant governor, "in a tough place."

"It seems that some of the moderate Republicans that she and other candidates were banking on just aren't Republicans anymore," he said.

Thus, the survey says, the fact Guadagno's campaign has taken a Trump-like right turn on immigration in recent weeks makes sense.

While 94 percent of likely New Jersey voters who still see themselves as Democrats say they disapprove of Trump, 76 percent of self-identifying Republicans say they approve of the job he's doing, the poll shows.

Political experts say Guadagno appears to be trying to shore up support among the GOP base in what is expected to be a low-turnout election.

Of registered Republicans who now disapprove of Trump, 30 percent say they're still Republicans, but 59 percent say they're now Democrats.

"While Trump still has pretty good approval numbers among New Jersey Republicans, that's partly because Republicans who don't like him have left the party," Cassino said. "There's been some replacement from former Democrats who like Trump, but the end result is a smaller, more uniform party."

All polls have shown Guadagno trailing Democratic nominee Phil Murphy by double digits in the Nov. 7 election to succeed Republican Chris Christie as governor -- though the race has been tightening.

The FDU poll was conducted via phone from Oct. 11 to 15 with 658 likely New Jersey voters. The margin of error was plus-or-minus 4.5 percentage points.

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