One of the biggest players in House Republican elections has, so far, committed zero dollars to Rep. Barbara Comstock’s race in Northern Virginia — among the most competitive contests this fall.

The Congressional Leadership Fund, a super PAC tied to retiring House Speaker Paul D. Ryan (R-Wis.), has reserved $60 million in advertising time on behalf of Republican candidates in dozens of races throughout the country, but none are in Virginia.

Comstock is seeking a third term — challenged by Democratic state Sen. Jennifer Wexton of Loudoun County — in an election that will help determine whether Republicans maintain control of the House.

The suburban district is home to the kind of affluent, educated voters who polls show disapprove of President Trump, and Wexton is hoping they will help propel her past Comstock.

In May, the Cook Political Report gave the edge to Wexton when it moved the race from toss-up to “Leans Democrat.” Just two weeks after Wexton won the Democratic nomination, before any campaigning had begun in earnest, a Monmouth University poll found the Democrat ahead of Comstock by 10 points.

But Comstock outperformed Trump in the district in 2016, is an exhaustive campaigner who spent her June birthday at community events and a prolific fundraiser — all factors that make her formidable.

CLF declined to say why it isn’t spending on behalf of Comstock, but noted that plans could change before Election Day.

“Nobody works harder than Barbara Comstock,” CLF spokeswoman Courtney Alexander said. “Anyone who would bet against her is foolish, and CLF is closely monitoring the race.”

Others are backing Comstock.

The National Republican Congressional Committee (NRCC) made its largest reservation for television advertising time, $6.4 million, for Comstock in the expensive Washington media market. Virginia’s 10th District spans the Washington suburbs of Loudoun, Prince William and Fairfax counties and reaches as far west as Appalachia.

The NRCC plans to spend the same amount in Minneapolis, where Rep. Erik Paulsen (R) faces a competitive race; CLF made a $2.8 million reservation for Paulsen.

The CLF and NRCC can’t coordinate their activities, but they often take cues from each other, based on how much TV and digital ad time they reserve.

Before she was elected to Congress, Comstock built a national profile in GOP politics for investigating Bill and Hillary Clinton and for professionalizing the opposition research operation at the Republican National Committee.

She has tapped that network to raise more money than other vulnerable Republicans. She had $1.7 million cash on hand by the end of June, which was more than double Wexton’s war chest at the time.

“She’s one of our strongest incumbents,” NRCC spokeswoman Maddie Anderson said. “We do acknowledge that it’s going to be a fight. We don’t shy away from fights like that; neither does she.”

The latest public polling in Virginia’s 10th District shows that 53 percent of potential voters disapprove of the job Trump has done and nearly half of voters intensely disapprove.

Nearly 8 in 10 of all potential voters said it’s very important or somewhat important to them to cast a vote that reflects their attitudes about Trump, the June poll by Monmouth University showed.

That’s why Democrats are working to tie Republican incumbents to Trump while Republicans like Comstock are focused on local issues in hopes of burnishing a brand distinct from the president.

“That Donald Trump and the NRCC would try to bail out Barbara Comstock is no surprise,” Wexton’s campaign manager, Ray Rieling, said in a statement. “She’s voted with him 97% of the time and now she’s being paid back for putting the President’s agenda over the interests of her constituents.”

This week, Comstock wrote a column in a Loudoun newspaper about the scourge of Lyme disease . She has targeted the MS-13 street gang, which is active in the capital region, and, with all the federal workers and contractors in her district, she is against government shutdowns.

Two independent rating agencies say the race leans toward Wexton, while Nathan L. Gonzales of Inside Elections considers it a toss-up — for now.

“Some Republicans can’t fathom Comstock losing because they see her as a solid member who raises a bunch of money and is a hard campaigner,” he said. “But the truth is that Comstock can run a perfect campaign this fall and still lose.”