Keeping control of the House would validate President Trump's governing style and mean full speed ahead for Hill Republicans to move his agenda.
But what if that doesn't happen?
But Trump earlier in the day appeared to distance himself from the fate of House Republican candidates.
The Daily Beast has examined that "unthinkable" scenario in some depth.
But with Trump in the Oval Office, she said she felt a responsibility to fight for issues like protecting the Affordable Care Act, "which I feel very proprietary about", as well as making sure there's "a woman at the table". Trump's enemies are gambling everything on winning.
The predictive model at FiveThirtyEight now projects an 88 per cent chance of them winning the seats required.
Healthcare and immigration were the top issues on voters' minds as they cast their ballots, according to an exit poll survey conducted by the Associated Press, and 64% of those surveyed said Trump was a factor in their voting choice. It all depends on how accurately they have predicted voter turnout.
Donald Trump is a factor for 65% of American voters - and of those, 39% said they oppose him versus only 26% in support.
OneNewsNow is working alongside its sister organization, American Family Radio, to provide live election night coverage from Tim Wildmon, president of the American Family Association, and Fred Jackson, news director of American Family News, as well as other familiar AFA voices.
Trump has been beating the drum against a caravan of migrants from Central America that is vending its way through Mexico to the United States border.
"The drumbeat you hear across America is people voting", Democratic Leader Nancy Pelosi said as polls opened Tuesday.
The party hopes younger voters, suburban moderates and minorities will be drawn to the polls to react against the president's rhetoric. "If you want strong borders and safe communities vote for Republicans". Florida and Georgia, meanwhile, could make history by electing their states' first black governors - and leading Democrats such as former President Barack Obama made special pitches for Andrew Gillum in Florida and Stacey Abrams in Georgia in the final days.
They need to pick up two dozen seats to claim the House majority. What if all the pollsters and pundits have missed a surge of silent Trump supporters? It will draw a lot of attention, but national Democrats caution not to read too much into a loss there, because Trump won it by 15 points.
Sanders offered a less restrained version of progressivism, which resonated with millions of Democratic voters.
Throughout the campaign, Trump has been tested out other explanations - pointing to historical headwinds for the party of an incumbent president and complaining about a rash of GOP retirements this year. "But it could be good for Trump - for his own personal political goals".
The airtight House contests are scattered across the country: Among them, Democrat Abigail Spanberger is challenging Republican Rep. Dave Brat in Virginia's 7th Congressional District; Democrat Danny O'Connor and Republican Troy Balderson are rematching in Ohio's 12th Congressional District; and Democrat Harley Rouda is challenging longtime Rep. Dana Rohrabacher in California's 48th Congressional District. The Tea Party movement grew as a response to that, propelling Republicans to a crushing victory in the midterms that year.
Democrats are trying to hold 10 Senate seats in states where Trump prevailed in the 2016 election, including Tennessee.
Democrats are acutely aware of the risks they are facing this time around.
On the Senate side, Indiana Democrat Joe Donnelly's fate will likely be critical to Senate control.
When Clinton lost in 2016, the candidate and fellow Democrats responded with shock and anger at how wrong the polls were.
Obama has been their most effective voice in this midterm campaign, but he has already served two terms as president.
"I'm not going to get into the specifics of the investigation", Kemp told reporters.
"He is kind of a towering figure in the party". Elizabeth Warren, New York Sen.
Others, like former MA governor Deval Patrick, California Senator Kamala Harris and former vice president Joe Biden, have been a little more active.
Both parties have a chance, if only a slim one, for an upset in the respective chambers where they're playing as underdogs.
Djokovic and Federer win to set up Paris Masters semifinal
After the two players held their serves for 4-all, Khachanov broke for the first time before bagging the first set 6-4. The Serb leads head to head meetings 24-22, he won the last match at the Cincinnati final this year in straight sets.
Smart home security needs to be a priority reveals Mirai.
This is why they are able to potentially cause so much harm, and why they are such a possibly lucrative target for attacks. Manufacturers are also focussed on keeping costs down in order to attract consumers, and security is not cheap.