RICHMOND — Virginia Democrats Tom Perriello and Ralph Northam are battling in a very close contest for the party’s gubernatorial primary, with divisions reemerging from last year’s Democratic presidential race, according to a new Washington Post-Schar School poll.

Democratic likely voters say Perriello’s endorsements by Sens. Bernie Sanders, I-Vt., and Elizabeth Warren, D-Mass., icons of the national progressive movement, carry at least as much weight as Northam’s support from Gov. Terry McAuliffe and nearly all other Virginia Democrats in Congress and the state legislature.

With less than one month before the June 13 primary, 40 percent of likely Democratic voters support Perriello, while 38 percent support Northam, a difference that is well within the survey’s range of sampling error. Perriello is a former congressman, and Northam is the state’s lieutenant governor.

More than 2 in 10 Democratic voters are undecided or have no current preference, a sign of fluidity leading into the final weeks before the June 13 primary, according to the poll co-sponsored by The Post and George Mason University’s Schar School of Policy and Government.

Among the broader group of Democratic-leaning registered voters, Perriello holds a slight edge over Northam, with 35 percent support to Northam’s 29 percent.

Northam’s supporters are more apt to fit the profile of likely voters, though — a factor that could prove decisive given that fewer than 10 percent of voters have participated in nonpresidential primaries in the past decade.

Age is a clear dividing line in support, with Perriello, 42, leading Northam by 20 percentage points among Democratic-leaning registered voters ages 18 to 39, while Northam, 57, leads by 16 points among those ages 65 and older. The two run more evenly among voters in between.

As one of only two gubernatorial races nationwide this year (the other is in New Jersey, which is less competitive), Virginia has drawn national attention as a proving ground for how Democrats move forward after Hillary Clinton’s defeat in November.

Perriello’s upstart candidacy has attracted national money and national media as he bashes President Trump at every opportunity, while Northam has patiently built support within the state and has campaigned on his ability to work with the Republican-controlled legislature.

Opposition to Trump clearly resonates with Virginia voters, only 36 percent of whom approve of his performance, according to the poll.

Perriello leads by 18 points among Democratic-leaning registered voters who wanted Sanders to win the party’s presidential nomination last year, while Clinton voters split 35 percent for Northam and 34 percent for Perriello.

Judging from last year’s outcome, a Sanders strategy would seem risky in Virginia. Clinton beat Sanders by nearly 30 percentage points in the state’s primary, though voters then were also split along generational lines. Exit polling showed Sanders won nearly 7 in 10 voters under age 30, while Clinton won clear majorities of older voters.

But the poll suggests that Perriello’s Sanders-like approach is finding traction. A 57 percent majority of Democratic likely voters say the Sanders and Warren endorsements make them more inclined to back Perriello. That’s slightly higher than the 50 percent who say the support from McAuliffe and other Virginia Democratic officials makes them more likely to back Northam.

That might suggest a shift in the state party.

“In the past, the Democratic Party of Virginia has always proudly bucked against the more progressive trends on the national party side,” said Mark Rozell, dean of the Schar School. “They’ve always had their success when they projected a more moderate image than the national party. I think things have flipped in some respects. We’re seeing a much more progressive wing of the Democratic Party active in Virginia.”

Northam and Perriello agree on most major issues and are seen by voters to possess similar attributes. But Perriello has a slight edge in the perception that he could stand up to Trump (38 percent to 30 percent), while Northam has a similar edge in perception that he could work with state Republicans (38 percent to 31 percent). Still, those results are within the poll’s range of sampling error.

There are a couple of key regional differences. Perriello enjoys a massive advantage in the southwest part of the state, where 58 percent of Democratic-leaning registered voters say they support him compared with 20 percent for Northam. Perriello is from Charlottesville and represented the rural 5th District during his single term in Congress.

Northam, who represented Norfolk in the state Senate, holds a smaller edge in the Hampton Roads region, with 40 percent support compared with 28 percent for Perriello.

The two are vying to take on one of the three Republicans running for that party’s nomination in the primary. Those candidates are former Republican National Committee chairman Ed Gillespie of Fairfax County, state Sen. Frank Wagner of Virginia Beach and Prince William County supervisor Corey Stewart. The poll found Gillespie with a commanding lead in that primary battle.

The Post-Schar School poll was conducted May 9 to 14 among a random sample of 1,602 Virginia adults reached on cellular and landline phones. The margin of sampling error for individual percentage results is plus or minus 4.5 points among the sample of 654 Democratic-leaning registered voters and six points among the sample of 351 likely primary voters. The range of sampling error for the difference between candidates’ support is 10 points among likely voters.

Washington Post staff writers Emily Guskin, Fenit Nirappil and Laura Vozzella contributed to this report.