Polls in the US have just opened in the first handful of states on the east coast, as Americans prepare to vote in the first national elections since Donald Trump captured the White House in 2016.
By the time most Australians wake, there will have some of the early exit polls, giving a better idea of trends emerging.
The first signs will come from key congressional races on the east coast in suburban Virginia, New Jersey, Florida and New York, however this will likely be a long day.
If the Republicans hold onto those east coast seats the Democrats will put their hopes in seats in Texas, Arizona, California and Washington.
Polls in most states close between 6pm and 8pm (local time) with official results expected in the hours after that.
By the time the sun goes down in Australia, there should have a good idea of what the future holds for the US, Australia and the western world.
The first national elections since Mr Trump entered the White House will be a referendum on the polarising Republican president and his hardline policies, and a test of whether Democrats can turn the energy of the liberal anti-Trump resistance into victories at the ballot box.
'Everything we have achieved is at stake tomorrow,' Mr Trump told supporters on Monday night in Fort Wayne, Indiana, at one of his three rallies to stoke turnout on the last day before the election.
All 435 seats in the US House of Representatives, 35 US Senate seats and 36 governorships are up for grabs on Tuesday.
Democrats are favoured by election forecasters to pick up the minimum of 23 House seats they need for a majority, which would enable them to stymie the president's legislative agenda and investigate his administration.
Republicans are expected to retain their slight majority in the US Senate, currently at two seats, which would let them retain the power to approve US Supreme Court and other judicial nominations on straight party-line votes.
In a last-minute controversy, NBC, Fox News and Facebook on Monday pulled an ad by Trump's campaign that critics had labelled racist.
The 30-second spot featured courtroom video of an illegal immigrant from Mexico convicted in the 2014 killings of two police officers, juxtaposed with scenes of migrants headed through Mexico.
Critics, including members of Mr Trump's own party, had condemned it as racially divisive. CNN already had refused to run the ad, saying it was 'racist.'
Voter turnout could be the highest for a midterm election in 50 years, experts predicted.
During a six-day blitz to wrap up the campaign, Mr Trump repeatedly raised fears about immigrants, issuing harsh warnings about a caravan of Central American migrants moving through Mexico toward the US border.