What's likely to happen?That's unlikely, by all accounts, because the map is so friendly for the GOP.
"In addition, the geographic distribution of the House implies that Democrats will need to win the popular vote by 5- 6pp to win a majority in the chamber". Around 30 races considered tossups by the Cook Political Report are still "startlingly close", according to interviews carried out by the Times and Siena College.
The party of a first-term president tends to lose congressional seats in his first midterm. The once strong Republican stronghold went to Hillary Clinton in 2016.
Should Democrats win control of the House, as strategists in both parties suggest is likely, they could derail Trump's legislative agenda for the next two years.
Mr Trump was making his closing argument to voters in Ohio, Indiana and Missouri.
In the week leading up to Tuesday's elections, Trump said he was optimistic about the outcome for the Republican Party, while at the same time using fear tactics to try to gain more support for his party. Democrats have a lengthy list of their own priorities they would like to vote on such as lowering prescription drug costs.
That environment still might not be good enough to deliver the Senate, though. Republicans, who have 51 seats, have a six in seven chance of retaining control. Heidi Heitkamp, a Democrat, in North Dakota.
All five Senate vacancies are Republican-held seats, including two in suburban Philadelphia and one each based in suburban Pittsburgh, and Blair and York counties.
Instead of running for re-election, Republican Assemblyman Dean Murray is running for the seat being vacated by state Sen.
The Democrats have rolled out their biggest gun: former President Barack Obama, who travelled to Virginia on Monday to get out the vote for its candidates. Aided by Republican retirements and an unprecedented flood of donations, majority from women, they appear to be almost guaranteed to gain at least somewhere in the mid-to-high teens.
In the Senate, where polls show the Republicans have an 83.2 percent chance of keeping control, the bookies are also betting on a blue wave.
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. "We are the Democratic Party", he said.
"The US Congress holds midterm elections on Tuesday and the Democrats are hoping to break their grip on the levers of power, according to analysts at Westpac".
He made the comments before a three-state rally blitz in a final push to keep Congress in Republican hands and prevent any potential losses that could change the course of his presidency. And Trump could set his sights on ousting Attorney General Jeff Sessions and other key figures at the Justice Department, possibly ending the department's investigation of Russia's attack on the 2016 election. And it wouldn't be wrong.
Democrats are most optimistic about the House, a sprawling battlefield extending from Alaska to Florida. FiveThirtyEight has them at a 1-in-8 shot.
"If you do see a turn against Democrats in Midwestern states such as in and Missouri, I think it is fair to say that the Republicans who are winning in those places are probably going to be more critical of trade, whereas the Democrats in those states are going to be a more centrist wing of the Democratic party", Hurl explained.
Republicans believe those issues, will help maintain control of the Senate. "Deplorable is adorable", read a T-shirt worn by a Trump supporter at his rally. It wouldn't necessarily be a resounding affirmation of Trump - these are only red states the GOP would be winning - but it would lead to some real, justified soul-searching. Even in the nine midterm elections when the president's approval rating was above 50 percent, his party still lost an average of 14 seats.
Turnout is expected to be high. It has not been unusual for a Democratic campaign event to occur with no reference to the president.
All 435 seats in the US House are up for re-election.
"These rallies are the best thing we've done". Let's see what happens, ' Trump said.
What it would mean: The same as above - chaos - except less specifically partisan.
"We feel like he's working to resolve all the problems that we are so frustrated by", Webb said.
ABC News' Political Director Rick Klein and Chief White House and Washington Correspondent Jon Karl spoke with Deputy Political Director MaryAlice Parks and Senior National Correspondent Terry Moran about what to expect on Tuesday on this week's Powerhouse Politics Podcast.