Voters in the affluent Northern Virginia suburban district have been represented by a Republican in Congress for 60 of the past 66 years.

Dow Jones Industrial Average futures declined in overnight trading amid news of the Democrats picking up their first House seat. Dow futures were last lower by 80 points.

The race was the first House seat to flip Tuesday evening from a Republican to a Democrat, and it was widely viewed as a barometer of Democrats' potential strength. The results were called in the early evening, after Wexton posted a double-digit lead over Comstock across large swaths of the district.

This year, however, shifting political winds across the state collided with President Donald Trump's unpopularity, turning the district into a prime pickup opportunity for Democrats.

In a year which has proven difficult for many incumbent Republicans, Comstock's odds looked especially bleak. From the start of the campaign, Wexton has maintained a commanding lead over Comstock in polls, averaging about 7 percentage points ahead.

Trump also likely contributed to Comstock's weakened support among voters. In the 2016 presidential race, Trump lost the 10th District to Hillary Clinton by 10 points. A recent Monmouth poll found that the president's approval rating in the district was underwater by 11 points.

Despite the prevailing political forces, Wexton mounted a hyper-local campaign, and focused on issues like health care and gun violence prevention. As a career prosecutor, Wexton was also well-positioned to defend herself against GOP attack ads portraying Democrats as weak on crime and national security.

By mid-October, Democrats were so confident that Comstock would lose that in mid-October the party's campaign committee canceled nearly $1 million worth of advertising it had reserved earlier in the year for Wexton. Instead of spending the money to boost Wexton, the party decided to redirect it to Democrats in congressional districts where the race appeared closer than it did in the 10th.

Wexton won the race despite being one of only a few Democrats in tight races who raised less money than their Republican opponent. As of Sept. 30, Comstock's campaign had raised $5 million, while Wexton reported having raised $4.6 million.