An influential Democratic House super PAC is cancelling nearly $1 million in ad buys in Virginia's 10th district, signaling that Democrats are increasingly bright eyed about their chances of ousting Rep. Barbara Comstock Barbara Jean ComstockLive coverage: House holds third day of public impeachment hearings Gun debate raises stakes in battle for Virginia legislature Progressives face steep odds in ousting incumbent Democrats MORE (R-Va.).

A source familiar with the buys said that House Majority PAC (HMP) pulled the plug on a roughly $470,000 reservation the week of Oct. 9 and cut about $510,000 from a reservation the week of Oct. 23.

The move by HMP suggests that Democrats are optimistic about Virginia state Sen. Jennifer Wexton's chances of defeating Comstock in November and may be looking to shift resources to other areas.

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Comstock's northern Virginia district has been represented by Republicans for more than three decades.

But Democrats are bullish about their chances of flipping the district in November, energized by shifting demographics, President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE's unpopularity and the fact that Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE won there by 10 points in 2016.

A Monmouth University poll in June gave Wexton a 9 point lead over Comstock in the race. That same month, The Cook Political Report, an election handicapper, moved the contest from the "toss-up" column to "Lean Democrat."

But both parties are spending hundreds of thousands of dollars in the race, and internal polls on both sides show a tighter race than the one reflected in public surveys.

Democrats are gunning for a so-called "blue wave" in November in hopes of recapturing the majority in the House and, possibly, the Senate. The party needs to gain at least 23 seats to win control of the House.

--Reid Wilson contributed to this report.

--Updated at 10:42 p.m.