The 2016 presidential campaign taught the world one thing: opinion polls can't be trusted.
Demographics have changed. Communications have changed. Politics has changed. The electoral system has not.
The polls weren't entirely wrong: Candidate Hillary Clinton won a majority of the one-vote one-value popular vote (with a margin of 2.1 per cent or 2.9 million votes). But, under the US electoral system, that doesn't matter.
It's about winning the necessary number of "points" allocated by an Electoral College system. And that means securing a few key swinging towns and suburbs.
Just eight of the 50 states of the Union held the nation's future in their hands.
Arizona. Florida. Georgia. Michigan. Minnesota. North Carolina. Pennsylvania. Wisconsin.
Even among this core group, a vote in Florida or Pennsylvania counts for more than in the others.
As the count stands at the moment, Michigan, Pennsylvania, Wisconsin and Georgia are too close to call and we may not get a result tonight.
There is now a chance of an Electoral College tie of 269 to 269.
What the polls say
With voting now closed across the US, people are now anxiously awaiting results in Nevada, Georgia, Michigan, Pennsylvania, North Carolina and Wisconsin to determine whether Trump will remain in power.
According to the polls, the President leads Biden 57-42 in Pennsylvania; 53-45 in Michigan; 51-47 in Wisconsin; 51-48 in Georgia; 50-48 in North Carolina and 52-45 in Maine's second congressional district.
Biden, meanwhile, has a 51-46 lead in Nevada; 52-46 lead in Arizona and 51-49 in Maine.
What happens if it's a tie
Suppose the popular vote is split 50/50 between Trump and Biden. In that case, the US National Academy of Sciences says Trump has an 88 per cent chance of winning the presidency. If Biden wins 52 per cent, Trump is still almost sure to keep his job. But if Biden gets 53 per cent, then the US is in for a bitterly tight presidential fight.
"If (Trump) falls just short of replicating his 2016 showing, the country could be plunged into a dangerous political and legal struggle combining the worst features of 2000 and 1876," states US governance analyst William Galston of the Brookings Institution.
Analyst Elaine Kamarck, also of the nonpartisan think-tank the Brookings Institution, says the US Constitution anticipated a tied vote. It just didn't predict the partisan state of US politics.
"If there is no winner in the Electoral College, Article 2, Section 1, Clause 3 states that the decision goes to the House of Representatives while the Senate picks the vice president," Kamarck writes. "But the voting in the House is different from the Senate."
The US Senate gets to vote for a vice president. Each senator receives one vote.
The House of Representatives gets to vote for the president. But, regardless of the size of each state represented, each state gets just one combined vote. And a president needs only 26 votes to win.
"If the presidential race should end up in the House the outcome would depend on which party controls the state's delegation," says Kamarck.
At the moment, the Republican Party dominates 26 delegations. The Democrats hold 23.
"But the Congress is sworn in before the Electoral College votes are read out in the Senate. In the case of a tie, it will be the next Congress – not the current Congress – that votes on the presidency."
But this is 2020. If things can get messy, they will.
Two states are balanced on a knife-edge between Republican and Democrat control. That means a delegation tie is also a distinct possibility.
"A handful of 2020 congressional elections could decide the presidential election," Kamarck notes.
According to the Brookings Institution, Pennsylvania and Florida could end up having a decisive say in who will be the next president. Specifically, Pennsylvania's 10th and Florida's 15th Congressional districts.
Both are hotly contested. The outcome of both will determine which way their entire state tips.
Pennsylvania's 10th: "The district has a PVI score of +6 Republican, meaning that in recent elections it tends to vote for Republicans. But recent polling suggests a neck and neck race," Kamarck says.
Florida's 15th: "Like Pennsylvania's 10th Congressional District, Florida's 15th tends to be Republican. But (Democrat) Cohn is running slightly behind (Republican) Franklin and within the margin of error".
If Democrats win both, the House of Representatives state delegate vote will be split 25-25.
Combine that with an Electoral College tie of 269–269, and you get … a constitutional crisis.
"What if the tied Electoral College race results in a tied race in the House of Representatives?" Kamarck asks. "The House keeps voting until someone gets 26 votes. If the House can't elect a president by Inauguration Day, the person elected vice president by the Senate becomes the acting president until the House manages to select a president."
Galston points to a history of controversy as an indicator of the future if this scenario unfolds.
"In this event, the state that most observers believe has the highest potential for electoral delays and snafus in counting mail-in ballots would determine the outcome of the race (Pennsylvania). This would all but guarantee a replay of the Florida controversy in 2000 that ended with Bush v Gore, but with a much higher level of partisan polarisation, more intense divisions over the legitimacy of the Supreme Court, and heightened threats of civil disorder."
Against the odds
"The 2016 election was a bracing reminder that the presidency is won or lost in the states and not in the national popular vote," Galston says. "Can (Trump) repeat this feat in 2020? Yes. Can he do it if he loses the national popular vote by a larger margin than four years ago? Probably not."
And there are four other tight congressional seat contests: two in Iowa, and another two in Minnesota. Flips in any of these will also alter the balance of the equation.
This means a tie for both the Presidential race and Representative delegate vote is not probable. It is, however, a disturbing possibility.
"While it may not reach the level of rancour following the disputed 1876 election — when the post-Civil War Reconstruction era came to its bitter end — it could make the disputed 2000 election look tame by comparison," Galston concludes.
With partisan politics threatening to tear US politics apart, the implications of the unbalanced US voting system must be anticipated: It could swing to the advantage of either contender.
"These scenarios are worth pondering if for no other reason than that they point out how the small-state politics that powered negotiations at the Constitutional Convention in 1787 don't meet the needs of America in 2020," Kamarck concludes. "In the 21st century, we have had two elections where the winner of the popular vote did not become president because of the Electoral College. Perhaps it is time to abandon the Electoral College for once and for all before we get into another mess."
• Jamie Seidel is a freelance writer