There are key races right off the bat with the Georgia governor's race, the Indiana Senate race and House races in Virginia and Kentucky, in particular.
Polls began at 6 p.m. eastern in parts of in and Kentucky, capping off a long day of anticipation. "We have added almost 500,000 manufacturing jobs to our economy - jobs that many self-proclaimed experts said would never return", Trump wrote in an op-ed for Fox News. But the closeness of the toss-up races - Republican Sen. Both Republicans and Democrats are energised.
"The message that I'm going to send is: We're not okay with the direction that this president is leading our country", said Rory Mabin, a 34-year-old Chicago resident who votes in every midterm election. Senate Republicans can continue to confirm judges at record rates.
Firstly, it would mean the party could block legislation proposed by the president. In early voting in Florida, for instance, 40.1 per cent who voted early were registered Republicans, and 40.5 per cent registered Democrats, said media reports.
Regardless of the numerical outcome, the fault lines in the United States look set to become even more apparent - divided between a liberal-moderate electorate concentrated in urban and coastal areas who mostly despise the President and a conservative-religious-blue collar voters spread across a vast swathe in the middle of the country who broadly love him.
Here comes the first big wave of races - nearly 30 competitive House races, five competitive Senate races and seven big ones for governor. He's been spending a lot of time in New Hampshire.
- Minimum wage increases are on the ballot in two states. Democrats could also make significant progress in the investigations of Trump's possible collusion with Russian Federation and of his tax returns.
Republicans were also being challenged outside Norfolk, where Rep. Scott Taylor faced Elaine Luria in the GOP stronghold.
Their votes are crucial to Democratic hopes to retake the Senate and sweep to victory in the House. And he has the most to lose should either chamber flip to Democrats, who will use control of committees to investigate the president and his Cabinet.
As for Republicans, what has the GOP done with control of the legislature for the past two years, with the exception of a single unpopular tax cut?
Just one state closes this half hour.
The final polls varied, but they were generally good for Democrats. The former president tweeted the vote "might be the most important of our lifetimes".
The Senate consists of 100 members, two from each state. Results from other key states like Texas, Michigan and Pennsylvania will begin to roll in between 8 p.m. and 9 p.m. Heidi Heitkamp as the most vulnerable incumbent.
The Republican Party is expected to retain its majority in the Senate. But now the Democrats are harnessing military patriotism too.
Of the 35 seats up for grabs, 26 are held by Democrats and nine by Republicans. Democrats are likely to flip the governor's mansion in MI, and are hoping to finally oust Wisconsin Gov. Scott Walker, but that race is another true toss-up. The closeness of the result is such that the seven races within four points in California, Maine and Washington could be determinative. Democrats need to gain 23 seats to retake the House, and there are only 25 Republican-held House seats in districts that Hillary Clinton carried.
Iowa offers a toss-up governor's race and several House contests to watch.
Waiting to vote at a polling station on Tuesday morning in Miami Dade county, video editor Daniel Z., 52, described himself as an independent voter, and said: "This is an accident in democracy - that a reality TV guy is our president".
What time do polls close? .
Facebook also blocked about 115 user accounts after U.S. authorities tipped it off to suspicious behaviour that may be linked to a foreign entity, the company said hours voting began. Much of that has gone to boost turnout among younger voters, although he has produced a nationwide advertising campaign calling for Trump's impeachment.
"Democrats want to control everything and everyone". That had always been a GOP stronghold that flipped to Clinton in 2016. But if they don't win a House majority or if they do but lose a fair number of seats in the Senate, their failure to recapture the Obama-Trump voter will be a big reason why.
But as he touched down in IN on Monday, even Trump conceded that the House may slip from his party's grasp. Herrera Beutler is one of only three GOP Hispanic women in Congress.
That is reflected in the early vote totals for these midterms, which are high. The main Republican superPAC started spending to help shore him up.