TRENTON -- With less than two weeks left before the primary elections, a new poll shows Democrat Phil Murphy and Republican Kim Guadagno continue to hold double-digit leads in the crowded races for their parties' nominations to succeed Chris Christie as New Jersey's governor.

The survey from Stockton University, released Thursday, also suggests Guadagno is widening her lead over her closest competitor, state Assemblyman Jack Ciattarelli now that the number of undecided voters have begun to tail off.

The school actually released the results of two separate polls: one taken April 26 to May 1, before candidates took part in televised primary debates, and one taken May 16 to May 23, after debates were held.

In the Democratic race, Murphy, a former U.S. ambassador to Germany, leads with 34 percent in the post-debate survey, a 3-point drop from the pre-debate poll. Murphy was repeatedly attacked by his rivals in the primary debates.

Still, that's within the poll's 4.9 percent margin of error. And Murphy -- who has spent $18.4 million on the race, nearly four times as much the other 10 major-party candidates combined -- has triple the support of his closest rival: former U.S. Treasury official Jim Johnson.

Johnson is at 10 percent in the post-debate poll, a four-point jump from the pre-debate survey. After that, state Assemblyman John Wisniewski is at 9 percent (a 1-point increase), followed by state Sen. Raymond Lesniak at 4 percent (a 1-point drop), retired Teaneck firefighter Bill Brennan at 3 percent (a 1-point increase), and Tenafly Council President Mark Zinna at 1 percent (a 1-point increase).

The surveys show the percentage of likely Democratic primary voters who are undecided dropped from 41 percent before the debates to 33 percent after.

In the Republican race, Guadagno, the lieutenant governor under Christie the last seven years, leads with 37 percent of the vote in the post-debate poll -- an 8-point hike from the pre-debate survey and nearly double the support of Ciattarelli.

Ciattarelli is at 18 percent in the post-debate poll, a 1-point drop from the pre-debate survey. After that, Nutley Commissioner Steven Rogers is at 4 percent (the same as the pre-debate poll), businessman Joseph Rullo is at 3 percent (a 1-point drop), and engineer Hirsh Singh is at 3 percent (a 1-point increase).

The surveys show the percentage of likely Republican primary voters who are undecided dropped from 41 percent before the debates to 31 after.

Poll organizers said it appears Guadagno gained most of the previously undecided voters who now have made up their minds.

Sharon Schulman, executive director of Stockton's Hughes Center for Public Policy, said two things helped cut down on undecided voters: the recent debates and increased news coverage of the races.

But the new survey found only 14 percent of likely voters watched or listened to at least one of the debates.

Schulman argued it's been tough for the candidates to gain attention because of the focus on President Donald Trump's new administration.

"It's hard to break through when the news from Washington dominates coverage," she said.

The poll also shows 63 percent of all voters in the pre-debate poll said they would consider voting for an independent candidate. That increased to 66 percent in the post-debate survey.

Meanwhile, the post-debate poll found most of the candidates remain largely unfamiliar to more than half of likely primary voters.

Forty percent of Democratic voters remain unfamiliar with Murphy despite his lead. Wisniewski is unfamiliar to 58 percent, Lesniak 62 percent, Johnson 64 percent, Brennan 71 percent, and Zinna 85 percent.

Thirty-one percent of Republican voters are unfamiliar with Guadagno. Ciattarelli and the other candidates are unknown to more than 70 percent.

The primaries are June 6. The winners receive the Democratic and Republican nods in the race to succeed Christie, a term-limited Republican who is set to leave office in January.

The poll was conducted via telephone from May 16-23 with with 791 likely New Jersey registered primary voters who participated in the 2016 primaries. That included 403 Democrats and 389 Republicans. The margin of error was plus-or-minus 3.5 percentage points.

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