Americans are bracing themselves for a particularly momentous midterm election today at the halfway mark of President Donald Trump's term, with the Democratic Party hoping to gain enough seats, at least in the House, to roll back the Republicans' majority and stall Mr Trump's agenda.
In the final hours before the election, Mr Trump has criss-crossed the country, pitching for key candidates in critical states such as Florida and Missouri.
He has highlighted the promises he has kept - principally boosting the economy, installing conservative judges on the Supreme Court Bench, and getting tough with countries that have, in his assessment, been taking advantage of the United States for decades.
His messaging also focuses on his agenda, including promises of a further tax cut for the middle class.
The language of the campaign - on both sides - has been more personal and incendiary than in any campaign in recent memory.
Mr Trump, in particular, has played on a visceral fear of weak borders and caravans of migrants heading from Central America to the US, and of the bogeys of runaway crime and socialist "mobs", if the Democrats gain ground and stall his agenda.
At a recent rally, he called attention to his predecessor Barack Obama's middle name, which is Hussein - pandering to a long-running trope among conspiracy-minded conservatives that Mr Obama is secretly a Muslim.
Mr Trump has also urged the electorate to turn out and vote - a message put across even more vigorously by Mr Obama. He has been campaigning for the Democratic Party, focusing on preserving the Affordable Care Act and warning of attempts by the Republicans to strip welfare measures to find money to offset the soaring deficit.
Underlining the existential nature of the midterm contest, Mr Obama has also raised the ante, painting the election as a choice between two different Americas: one inclusive and embracing diversity, and the other narrow and exclusionary, and favouring corporate interests at the expense of ordinary Americans.
The party is banking on a bigger turnout than usual to boost its candidates. In this respect, the divisiveness and controversy that have been a deepening feature of America's political landscape - since at least 2016 when Mr Trump unleashed his aggressive campaign for the presidency, tapping old fault lines and pent-up resentments - appear to have energised voters.
Millions have already cast their ballots in early voting that has surpassed records for midterms, with numbers boosted by the young and in some cases, first-time voters.
In North Carolina, for example, 9.1 per cent of early voters were in the 18-29 age range, compared with 5.9 per cent in the 2014 midterms.
Support for the Republicans remains reliant on Mr Trump's core base - older, conservative, largely rural blue-collar white men and women.
But there are regional differences. In Florida, for instance, early Cuban immigrants lean towards Republican. Evangelical Christians are also a key constituency, seen to be happy with Mr Trump and Vice-President Mike Pence over their pro-life conservatism and the President's shifting of the US Embassy in Israel to Jerusalem.
In 2016, roughly a quarter of voters - 26 per cent - described themselves as white, born-again or evangelical Christians. But there are considerable numbers of African-American evangelicals as well. As many as 81 per cent of evangelicals voted for Mr Trump in 2016. Many controversies later, Republicans are hoping the support has not eroded.
Midterms have traditionally not been kind to the party in power. In the 2010 midterms, the Democrats, with Mr Obama in office, lost 63 seats.
This time, given the increased turnout and the rise of young and first-time voters, analysts see the Democratic Party as very likely to regain control of the House, but less likely to gain control of the Senate.
But opinion polls were wrong in 2016 and as the midterm election nears, most pundits have turned to hedging their bets. Many of the races are rated toss-ups, and close results may be subjected to run-offs or recounts.
Ultimately, the election is seen as a referendum on Mr Trump. Aside from Congressional and Senate races, the outcome of a slew of state gubernatorial races will also signal the mood of the electorate two years into Mr Trump's presidency, and two years before he seeks re-election in 2020.
"2018 is the Donald Trump Midterm. Americans will either want to put a check on Mr Trump or they won't," tweeted Dr Larry Sabato, director of the University of Virginia's Centre for Politics. "Even where Mr Trump isn't mentioned, he sets the stage and fills the stage."