It’s the final stretch for what has turned out to be one of, if not the most, hotly contested in the history of US presidential elections, with rivals Vice President Kamala Harris and former President Donald Trump locked in a dead heat.

Not a few are holding their breath as they await the results of a race with worldwide impact, but many of those awaiting the outcome, including Filipinos, are also quite befuddled about that critically vital thing that will ultimately determine who the next US president will be.

The thing to understand is that in the US, a candidate wins the presidency not by winning the majority of the national popular vote, but through a system called the Electoral College (EC).

Explains the US National Conference of State Legislatures: “When voters cast their ballots for a candidate for president of the United States, they are actually voting for the presidential electors selected by that candidate’s party.”

The names of the candidates, either “Donald Trump” or “Kamala Harris” on the ballot cast represent slates of electors — members of the Electoral College — who are pledged to vote for that candidate.

Its name aside, the EC is actually a process rather than a body. Under this system, voters in each state and the District of Columbia decide the outcome of a contest for their state’s electoral votes.

Each state is allocated a set number of electoral votes according to the size of its population. By securing a majority of the vote in a state, a candidate collects its allotted EC votes.

There’s a total of 538 EC votes, thus, a candidate needs at least 270 votes to win the presidency (with their running mate becoming vice president).

In mid-December following an election, EC members meet in all 50 states on the same day and cast their vote for president, with the results sent to Congress.

Congress then certifies the votes on 6 January. If there’s a tie, the House of Representatives, as required by the Constitution, will hold a contingent election to choose the president.

The perplexing EC system is as old as the US Constitution. In operation since 1789, it is the world’s longest surviving written Constitution.

Then, the US’s founding fathers had debated on who should be trusted to choose the nation’s leader, with some urging Congress (state legislators) to decide who while others argued for a more democratic (popular) vote.

The process is arduously complicated, which would fill tomes to detail out, but basically Suffolk University political science professor Rachel Cobb says that when the founding fathers “designed the system, they came up with the EC, not because they thought it was perfect, but because it was a way to get the Constitution passed, and it satisfied the concerns of both the very populous states and the less populous ones.”

For University of Wisconsin-Madison’s Elections Research Center director Barry Burden, the US election is really “51 separate elections, with each state and the District of Columbia having its own rules for running the election. Each state separately awards its electors (political parties in each state select the electors) and it’s up to the presidential candidates to win a majority of these electors’ votes to be elected president.”

In this election, surveys show an extremely tight contest between Harris and Trump and observers say final results will likely be determined in swing states Wisconsin, Pennsylvania, Georgia, Arizona, North Carolina, Nevada and Michigan.

ABC News analyses see Pennsylvania, among the swing states, as critical to the outcome of the election as it has the most electoral votes, at 19. Pennsylvania backed Biden in 2020, turning blue after the 2016 election when it went for Trump.

If Harris grabs the votes in Pennsylvania, along with Michigan, Wisconsin, plus one electoral vote in Nebraska — all of which Biden won in 2020 — she will gain 270 votes and win the race — no matter if she loses in the four remaining swing states.

Meanwhile, if Trump gets Pennsylvania along with the electoral votes in all the states that backed him in the last election, he would still need to win Georgia to come out on top.

A 269-269 tie in the EC vote is unlikely but not outside the realm of possibility (it happened only once, in 1824). If the votes are tied, the US Constitution calls for a contingent election, requiring the House of Representatives to elect the winner, with each state having a vote. Either candidate must have 26 out of 50 states on their side to get elected.

But here’s the thing — if the votes are tied, it is virtually all over for Harris, with Republicans in control of the House of Representatives.

And where is the popular vote in all of this? The hard fact, as far as Burden is concerned, is that “it’s a symbolic victory” that doesn’t matter in ultimately deciding who the next US president will be.

Twice in the last five US elections the popular vote went one way, and the EC vote went another. The same thing could very well happen this time.