Does Trump have a plausible victory route?

To the horror of many of us, pollsters and serious commentators have yet to write Donald Trump’s election chances off entirely. While Hilary Clinton is the clear favourite, her polling leads are not big enough to assume a Democrat landslide. Clinton is not well-liked, and even the possibility of a Trump presidency will not persuade some voters to support her. Trump is also an unprecedented candidate whose policies and rhetoric may appeal to disengaged white communities and traditional blue-collar Democrat-leaning voters.

So could he actually win? To do so, he must not only narrow the popular vote gap with Clinton, but also overcome the electoral college on voting day. The presidential electoral system sees states and the District of Columbia (D.C.) give a number of “votes” to candidates depending on their populations. The candidate who tops the poll in a state is awarded all of the “votes” (with the exception of Maine and Nebraska, which award their “votes” proportionally). There are 538 “votes” up for grabs, with a candidate needing 270 to win the election.

We will consider two things to map out a potential victory route for Trump: (1) how candidates are currently polling in all states and D.C.; and (2) historical voting patterns in states so we can make an educated guess as to how they will vote in November.

For point (1), we use recent state-level polling aggregated by the fivethirtyeight polls-plus forecast, which predicts voting behaviour based on recent polls and socioeconomic factors. We will use the standard “+/- 3%” margin of error rule to assign states and electoral college votes to candidates. In short, this rule assumes that a candidate’s true level of support is within 3% of the level predicted in a poll. For example:

If a poll finds support for Trump at 40%, it should be interpreted that his true level of support lies between 37% and 43%. If the same poll finds support for Clinton at 45%, it should be interpreted that her true level of support lies between 42% and 48%. This could mean Trump potentially has more support than Clinton.

States will therefore be awarded to candidates if their parties currently enjoy a lead higher than 6% as this will mean the +/- 3% rule is redundant.

The table below lists the states and electoral college votes the candidates would win, which we will refer to as the parties’ “foundations”. In terms of electoral college votes, Clinton’s foundation is much stronger than Trump’s, with 217 to 154 votes respectively. The Democrats do best in well-populated states — half of their foundations states have double-digit votes up for grabs — while Republicans perform better in more rural states. The combined foundations total 37 states plus D.C., meaning Trump needs to perform strongly in the remaining 13 states to overturn Clinton’s commanding lead.

Source of polling data: (5 Aug 2016)

How might these remaining states vote? For point (2), we look at how they have voted in previous elections to assess who they are likely to support in November. For this exercise, we will make the assumption that Trump can appeal to traditional Republican voters in ways that previous mainstream candidates have done.

The table below assigns six of the remaining 13 states to parties. Minnesota and Pennsylvania are awarded to Clinton as they form part of the “blue wall”: Minnesota has voted Democrat since 1976 and Pennsylvania since 1992. This gives her an additional 30 votes, leaving her only 23 votes short of victory. Trump gains four states: Arizona, which has voted Republican since 1952 apart from the 1996 election; Georgia, which has voted Republican since 1996; Missouri, which has voted Republican since 2000; and North Carolina, which has voted Republican since 1980 apart from the 2008 election. This gives him an additional 52 votes, leaving him 64 votes short of victory.

Source of polling data: (5 Aug 2016)

Current polling and historical state voting give a clear advantage to Clinton and the Democrats. The remaining seven states, detailed in the final table below, will be vital for Trump should the above scenario play out. All seven currently lean Democrat, albeit within the +/- 3% margin of error.

Source of polling data: (5 Aug 2016)

Two states are key here. Florida is the most important state mathematically: if Clinton takes it, the 29 electoral college votes take her beyond 270. Ohio is the most important state for the Republicans historically: no Republican presidential candidate has ever won an election without winning there. Trump must win both states to even stand a chance of overturning Clinton’s lead.

And even if he wins both, it is still advantage-Clinton as victory in three remaining states — Nevada, Colorado and Virginia — would still take her over the line. Betting markets favour her taking Nevada, which has voted for the winning candidate in every election since 1980.

In short, despite Clinton’s unpopularity and the supposed appeal of Trump’s unorthodoxy, the data suggests the Democrats are on course for victory in November. While a lot can change in the 90 plus days remaining — the email scandal headlines are not going away — current polling figures and the electoral college make a Trump presidency improbable…surely?!