Democrat Jennifer T. Vexton defeated Representative Barbara Comstock (R-Va.), Ending nearly four decades of democratic control of a basic North Virginia seat.
By exploiting President Trump's popularity, Wexton, a senator and former prosecutor, won 56% of the vote, compared to Comstock, who gained 44%, with almost all regions reporting.
He won with the depiction of the alliance as an ally of truce, who was offline with a well-educated and varied electorate that began moving the region to the left.
"The change comes to America and the change comes to Virginia 10 and this change came tonight!" Wexton told the hospitable fans at the winning party. "We demand a better nation, a nation where we face each other with dignity and respect."
Voters who have decided to send a Trump message have dismissed Comstock after nearly a decade representing parts of the 10th District, first as a political legislator and then for two terms in the US House.
Comstock took the stage at her party to cause applause.
"Success is never final, failure is never lethal, it is the courage to keep counting," he said, urging young volunteers not to lose their hearts.
She said she had told one of her granddaughters that they were going to Disney World, regardless of the outcome. "That's where we're going now."
After a few minutes of embracing her supporters, she threw a back door.
David Ramadan, a former political lawmaker close to Comstock, said the Trump destroyed the Republican Party and accused him of losing cofactor.
"There is no other way to say this, but that's the dirty mistake in the White House," he said.
Earlier this day, retired Loudoun County Michele Hoehner captured the mood of Democrats Activated: "Vote for them!" Voted for Wexton, Sen. Tim Kaine (D) – and change, he said. "The firearms are out of control, I'm tired of the evil."
Wexton was named wife "Barbara Trumpstock" and often shared a statistic from the FiveThirtyEight website that showed that Comstock voted with Trump 98 percent of the time.
In response, Comstock said that 82% of the accounts being tracked on the site were transferred on a bilateral basis or with the support of at least a few Democrats.
But Trump's influence in the elections was incontrovertible.
According to preliminary results from a survey by the Post-Schar School of Washington for people who voted in the 10th District, nearly 6 out of 10 voters said President Trump was one of the two most important players in their vote and favored Wexton vs. Comstock about 4 to 10 margin.
The 10th District includes Loudoun County and parts of Fairfax and Prince William, as well as the Clarke and Frederick counties and Winchester to the west.
Since Red is trusted, the region has moved to the middle and left in state and national games, making it more difficult for Republicans to stay alive, with the exception of Comstock.
Gerry Last, a 59-year-old engineer from McLean, voted for Commostock and Copenhagen Senate candidate Corey Stewart, who was convicted by Kaine. But it really saw it as a vote for the Trump.
"The country finally goes in a good direction," he said. "Trump is returning jobs, people are buying things again, I feel that I want to change jobs now, there are jobs available, where before I felt like I was stuck in the same position."
Democrat Hillary Clinton won the area with 10 points in the presidential race of 2016, but Comstock also won, trumped the Trump with 16 points, with relentless focus on local issues. Comstock had called for the Trump to leave the race after a film that appeared with him boasting women's stings.
A year later, the Democrats and antitrust officers dominated North Virginia, electing Governor Ralph Northam and expelling all the Russian state lawmakers who shared land with Comstock.
Democrats felt good about their chances from the start. Polls showed that Trump was unpopular in the region as a whole and that demographics shifted to their advantage with the most educated and diverse professionals moving more and more.
The national focus helped Comstock and Wexton raise nearly $ 5.4 million, with Wexton ahead.
External costs have also flooded the area. The teams spent about $ 5.9 million on behalf of Wexton and about $ 5.5 million on behalf of Comstock, according to the Center for Policy Awareness.
Although public polls showed Comstock to be back, the National Republican Congress Committee was trapped by her, who poured money into the fight when others, like the Congressional Leadership Fund, made a pass.
On the eve of the election, former President Barack Obama, with a box of donuts in hand, made a surprise visit to Fairfax to bring loyalists Wexton and Kaine.
Comstock, a former GOP agent who investigated Clinton in the 1990s, chose friends to raise money at the highest levels of national politics, from Vice President Pence to House President Paul D. Ryan (R-Wis.).
Shortly after Trump was elected, the Democrats built their campaign around the voter's excitement of 2017 and his direction in the Congressional struggle.
In previous years, the party had struggled to find at least one viable candidate to challenge Comstock, but this year more than a dozen serious candidates have expressed interest.
Wexton has won six directions for its legislative record and the power of approvals by Northam and Rep. Gerald E. Connolly (D-Va.) And the powerful Weapons Control Group, the Coalition for Strategic Violence.
Amit Suri, a 47-year-old doctor from McLean, voted in favor of Wexton making a statement about Comstock's ties with the National Union of Ducks, which gave her a score of A.
"It is a shame to see a country where the nurses are cut off and we can not yet talk about it," said Surrey.
In the general election, Wexton highlighted her personal story as a working mother with deep roots in the Loudoun area, the heart of the region.
A promotional video with her that led the two boys to and from school as they grew up with her achievements in the State Senate: "Helped mums gather their children's support", "targeted sexual offenders," "took the weapons away from domestic villains ".
Another ad led voters to know that Wexton voted in the General Assembly to broaden Medicaid, an important long-term goal for Democrats.
While Democrats believe Comstock is too conservative for the region, some Republicans believe it is too mediocre and faced a prime challenge from the right.
He won 61 per cent of the votes and turned to general elections that decided to persuade voters that they should be judged on their own records, not Trump's and GOP's.
Comstock, whose area includes tens of thousands of federal workers, opposed Trump's call for frozen pay and government shutdown, and voted against Trump's bill to abolish the law on affordable care.
Her ads called her "independent warrior for Virginia" and "independent Virginia voice" and assumed that GOP policies stimulated the economy.
She has also played her support for the victims of sexual harassment at Capitol Hill with an ad featuring a woman who lost a practice because she would not meet a congressman in his home just one night.
Wexton has questioned Comstock's commitment to the #MeToo movement, highlighting its support for her long-time friend and Supreme Court judge Brett M. Kavanaugh in view of Christine Blasey Ford's accusations in the confirmation process.
NRCC ads grabbed Wexton's vote for a budget that spurred massive toll rises despite its opposition to the toll plan and accused her of reducing charges against violent criminals.
The ad reported two cases where Wexton waived the charges as part of the opportunities.
None of these matters for Courtney Riddle, a 46-year-old businessman from Loudoun County, who normally votes for the Libertarian but went on this time with Wexton and Kaine.
"At his core," Riddle said, "we have to make a statement against our administration."
Michael Brice-Saddler, Steve Thompson and Debbie Truong contributed to this report.