Explainer: How the Electoral College works

By Dr Adrian Beaumont. Election Watch polls analyst

In US Presidential elections, the popular vote of the candidates is not decisive.  The outcome is determined by who wins the most Electoral College votes.

Each state receives a number of electoral votes.  There are 538 electoral votes in total, which make up the Electoral College, so the winning candidate needs 270 electoral votes (just over 50% of 538).

While the winner of the overall popular vote can lose the electoral college, this has only happened three times.  The last time this occurred was in 2000, when Democrat Al Gore lost the electoral college to Republican George W. Bush 271-266 despite winning the national popular vote by 0.5%.  It is only realistic for the popular vote winner to lose the electoral vote if the popular vote margin is less than 2%, and in most Presidential elections the popular vote winner has a landslide in the electoral college.

If no candidate wins at least 270 electoral votes, a complex system is used to select the President, but this has only happened once, in 1824.

Expected Electoral College votes based on current polling

The map below, from Electoral-Vote.com, shows polling current this week in all states.  The number of electoral votes expected for each state on November 8 is given below the two letter state abbreviation.  In the US, blue is the Democrats’ colour (Hillary Clinton), and red represents the Republicans (Donald Trump).  It is very unlikely that a candidate other than Clinton or Trump will win any electoral votes.

This polling indicates that Clinton would win 294 electoral votes, Trump would win 226 electoral votes and 18 electoral votes (those of Ohio) are tied.

US Electoral College map

Dark blue or dark red states are respectively where Clinton or Trump has a double digit poll lead.  In light blue or light red states, the lead is 5-9 points.  In white states with a blue or red border, the lead is 1-4 points.  Completely white states represent a polling tie.  The map ignores the Nebraskan and Maine complications (they are the exceptions to the rule that the winner-takes-all) by assuming that these states are winner-takes-all.

The map uses the US two letter abbreviations for all states. A list of all abbreviations can be found here.  The geographically small north-eastern states are represented by a column to the right of the main map.

Most of the north-eastern and Pacific coast states are reliably Democratic, while most southern states and low population prairie western states are reliably Republican.  Swing states are states that can go either way if the national vote is close.  The biggest swing states are Florida (29 electoral votes), Pennsylvania (20 electoral votes) and Ohio (18 electoral votes).

The electoral college system means that states regarded as safe for either side get little campaign attention, much like safe seats in Australia. Thus three of the four most populous states (California, Texas and New York) get little attention.

While Clinton still leads, the contest has tightened over the last couple of weeks.  On 23 August, Clinton had leads in states worth 343 electoral votes to Trump leads in states worth 195 electoral votes.  Furthermore, Clinton had leads of at least 5 points in states worth 320 electoral votes on 23 August.

I think the key reasons for the tightening is that Clinton’s emails and the Clinton Foundation have received renewed media attention over the last ten days, and both issues are damaging Clinton.  It had also seemed possible that Trump would tone down his hard-line immigration rhetoric until his speech in Arizona on 31 August.

How a state’s electoral votes are calculated

The US Congress (the national legislative body) has 435 members of the House of Representatives, and 100 Senators.  The 50 states have two Senators each, while House seats are awarded on a population basis, with the lowest population states getting one House seat each.  The highest population state, California, has 53 House seats.

A state’s electoral votes are calculated by adding that state’s House seats to its two Senators, so the lowest population states have three electoral votes each, while California has 55.  In addition, Washington DC, which has no voting representation in Congress, has three electoral votes.

Almost all states award their electoral votes winner-takes-all. That is, the Presidential candidate who wins more popular votes than any other candidate within that state will win 100% of that state’s electoral votes.

There are two minor exceptions to the above rule: Nebraska and Maine.  Both states award one electoral vote to the winner of each of that state’s House seats, and two to the state-wide winner.  However, Nebraska has just five electoral votes and Maine four.  At most ,two Nebraskan electoral votes and one Maine electoral vote could go to a candidate who did not win the state.  In practice, all of Nebraska’s House seats are more Republican than the nation, and all of Maine’s seats are more Democratic.  Obama won one Nebraskan electoral vote in 2008, but it did not matter as he won the Electoral College 365-173 that year.

Main image credit: Wikipedia


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