RICHMOND, Va. (AP) — In less than a month, Virginia voters will pick 100 people to represent them in the House of Delegates, races that will be closely watched as an early referendum on President Donald Trump's first year in office.

The elections also will be a test of whether Republicans can hang on in increasingly diverse, populous and liberal-leaning northern Virginia.

A surge of Democratic candidates unlike the party has seen in years is going up against Republican incumbents across the state, even in deeply red pockets. But many of the most hotly contested races are in Washington's growing suburbs, where the changing demographics and Republican retirements have made many seats competitive.

"I think it is going to become tougher and tougher (for Republicans) unless there are pretty dramatic changes in both parties," said Thomas Rust, a Republican and former longtime mayor of Herndon who held a northern Virginia seat in the House for 13 years.

In the past, Democrats have essentially ceded control of the House to Republicans, who have led the lower chamber for nearly two decades and currently have a 66-34 majority. The biennial contests typically draw far less attention than races for governor or the state Senate.

But many political newcomers have jumped in this year, at least partly motivated by Trump's victory. Sixty of the 100 seats are being contested on Nov. 7 by candidates of both major parties, more than in any year for at least two decades.

Democrats have candidates running in all 17 Republican-held districts where Hillary Clinton beat Trump last fall. Ten of those are in northern Virginia, where it's more expensive to run a campaign and where money has been pouring in.

Republicans say they're not worried. Their years in power have helped them build up a significant cash-on-hand advantage, and they say voters in local races care about local issues — not what's going on in Washington. They say their delegates are well known in their communities and have track records of success.

"You could see us hold everything," said John Whitbeck, chairman of the Republican Party of Virginia. "It wouldn't surprise me at all"

Still, he acknowledged tough contests in the northern Virginia races to replace retiring Del. Mark Dudenhefer and Del. Dave Albo and said the races in Prince William County are "very important" to the party.

The nearby 67th district, which includes parts of Fairfax and Loudoun counties, is another seat Democrats see as a possible pickup.

Moderate Republican Jim LeMunyon, a technology company entrepreneur, was first elected in 2009 to represent the increasingly liberal district.

That year, about 58 percent of voters in the district voted for Republican Bob McDonnell for governor. But in 2013, 51 percent voted for Democrat Terry McAuliffe over Republican Ken Cuccinelli, according to the nonpartisan Virginia Public Access Project. And in the fall, Clinton beat Trump there by 22 points.

LeMunyon, who didn't respond to the AP's interview requests, says in campaign materials that he's worked across the aisle to get a record number of bills passed and signed into law.

His opponent is Karrie Delaney, who owns a small consulting firm doing communications strategy for nonprofits, and has previously worked with kids in foster care and as a sexual assault crisis counselor.

She said in an interview that LeMunyon's votes against Medicaid expansion and full-day kindergarten show his willingness to take Republican party positions against voters' interests.

"For far too long, LeMunyon has been putting politics over the people," she said.

But former Republican Del. David Ramadan said he thinks LeMunyon will win comfortably, in part because of his relationship with constituents.

"It doesn't matter if Jim's a Republican or Democrat. To that voter, Jim's the guy who's at their door. Jim's the guy that writes them 20 times a year on transportation issues, which is their No. 1 issue," said Ramadan, who represented a district that included parts of Loudon and Prince William counties.

Susan Swecker, chairwoman of the Democratic Party of Virginia, says observers should take note of what happened in a special election for clerk of court in Prince William County earlier this year. Del. Jackson Miller, a member of Republican leadership, lost to Democrat Jacqueline Smith, despite outspending her more than 5-to-1.

"I think the winds of that kind of change are at our back," Swecker said.

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Associated Press writer Alan Suderman contributed to this report.