Designed to approximate proportional representation, this century the system has delivered two presidents who lost the US popular vote. Some say it gives a voice to rural voters, others say it disenfranchises millions.
Among the least understood yet most consequential elements of the US presidential electoral system is the body that actually casts the votes determining the next leader of the country: The Electoral College.
Written into the US Constitution in 1787, the body currently consists of 538 appointed electors, or delegates, with each state having the same number of electors as they have representatives in both houses of the US Congress. The least populous state, Wyoming, has 3 electors, whereas the most populous, California, has 55.
"Literally what you are doing when you vote in an American presidential election is you are voting for a slate of electors," says Ken Kollman, professor of political science at the University of Michigan and director of its Center for Political Studies (CPS).
"So when you vote for the Republican or Democratic Party you are voting for a slate of either Republican or Democratic electors. Those electors then, within each state, are part of a small version of the Electoral College and they will cast the votes for president after the popular vote is cast."
The Electoral College was a compromise between framers of the US constitution arguing Congress should elect the president and others who claimed a decentralized system would safeguard against the concentration of power.
The Electoral College is a filter between the one-person, one-vote ideal of the popular vote and the appointment of the nation's leaders.
With 48 states awarding electoral votes in winner-takes-all fashion (unit rule) it has become possible for candidates to capture the majority of Electoral College votes (270) by winning electorally close "swing" or "battleground" states rather than the national popular vote.
This has happened twice this century, with Republicans George W. Bush and Donald Trump winning the 2000 and 2016 US elections respectively, despite losing the popular vote.
Proponents of the Electoral College say it forces candidates to visit more of the country, not just its most populous areas.
"The argument is that if we went to the popular vote, candidates would spend all their time in the largest population centers. They would just spend their time in the biggest cities and would ignore the rural areas of the country. It's a little more complicated than that. They ignore vast portions of the rural areas of the country already — it depends on if you are in a rural area in a swing state. Then they pay attention to you," says Kollman.
Maine and Nebraska are the only states to award electors not by the unit rule but according to state popular and congressional district vote returns. This allows them to split electoral votes between candidates.
Electors are appointed by and vote in their home states "on the first Monday after the second Wednesday in December next following their appointment." This year they vote on December 14.
State electors then send their votes to Congress, which assembles for a joint session in the first week of January. The name of the winner is then read aloud by the incumbent vice president, acting in his role as president of the Senate. On January 6, 2021, that job will fall to Mike Pence.
The US Congress eventually tallies the electoral college votes. In 2017, it was then Vice President Joe Biden (at podium) who oversaw proceedings.
Critics say the Electoral College disenfranchises millions and gives disproportionate weight to voters in less populous rural states. According to US Federal Election Commission data, an Electoral College vote in Wyoming represents roughly 190,000 people, whereas a vote in California is divided among almost 720,000.
"More than half of the states have more influence through the Electoral College than they do through the popular vote," says Ken Kollman.
But he is quick to add: "The Senate is a much larger problem than the Electoral College in terms of giving more political weight to areas with smaller populations. The US Senate is a dramatically disproportionate body, meaning smaller states are vastly overrepresented in the Senate compared to larger states."
In 2016, Donald Trump won the "swing" states of Wisconsin, Michigan, Pennsylvania and Florida by razor-thin margins — the unit rule allowed him to put all 75 of their electors into the win column. This year his key demographic — non-college-educated white voters — is overrepresented in most battleground states.
Asked about the long-term Electoral College map, Kollman says: "The country is increasingly becoming geographically polarized by party. I don't anticipate that changing anytime soon."
"I think the major question that confronts the United States is how the Republican Party is going to adapt post-Trump? [In January or in four years], I think that is the largest question confronting the American party system."
Trump moved the party in an "isolationist, protectionist, nativist direction," says Kollman. "I think it is a major question whether the party will stay there or move back to where it was even five or six years ago, because all else follows from that," he says.
"But if the Republicans stay where they are and become a Trumpian party permanently, or at least for another generation, I think their prospects are very dim to win national office."