The US presidential election might be closer than the polls suggest (if we can trust them this time)

On the one hand, this year’s election seems to have historically low levels of undecided voters. But offsetting this is tremendous uncertainty about turnout and whose votes will be cast and counted.

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SOURCEThe Conversation

With less than two months until the US presidential election, Democratic nominee Joe Biden leads incumbent Donald Trump in the bulk of opinion polls.

But poll-based election forecasts have proved problematic before. The polls were widely maligned after the 2016 election because Trump won the election when the majority of the polling said he would not.

What went wrong with the polls in 2016? And is polling to be believed this time around, or like in 2016, are the polls substantially underestimating Trump’s support?


Read more: How did we get the result of the US election so wrong?


Swing states decide US presidential elections

US presidential elections are two-stage, state-by-state contests.

States are allocated delegates roughly proportional to their populations, with 538 delegates in total. The votes of Americans then decide who wins the delegates in the Electoral College.

In almost all states, the candidate who has the highest vote total takes all the delegates for that state. The candidate who wins a majority (270 or more) of the Electoral College wins the election.

Biden has been spending more time in the crucial state of Pennsylvania, where he holds a slim lead over Trump in many polls. Mary Altaffer/AP

For the fifth time in American history, the 2016 election produced a mismatch between the national popular vote and the Electoral College outcome. Hillary Clinton, the Democratic candidate, won nearly 2.9 million more votes than Trump, yet still lost the election.

Trump won states efficiently, by razor-thin margins in some cases, converting 46% of all votes cast into 56.5% of the Electoral College. Conversely, Clinton’s huge popular vote tally was concentrated in big states such as California and New York.

For this reason, election analysts focus less on national polls and more on polls from “swing states”.

These are states that have swung between the parties in recent presidential elections (for example, Michigan, Wisconsin, Pennsylvania, Florida and North Carolina), or could be on the verge of swinging (Arizona, Texas, Georgia and Minnesota).

These states — even as few as two or three of them — will decide the 2020 election.


Read more: Republicans have used a ‘law and order’ message to win elections before. This is why Trump could do it again


State polls currently point to a Biden win

As part of a large research project at the United States Studies Centre, we have compiled data from polling averages in all the swing states going back to 120 days before the election and compared them to the same time periods in 2016. Our goal was to provide a key point of reference to more correctly read the polls in 2020.

The charts for all swing states can be found here.

Our research shows Biden currently has poll leads in several states that went for Barack Obama in 2008 and/or 2012 and then swung to Trump in 2016, such as Florida, Michigan, North Carolina, Pennsylvania and Wisconsin. These five states are worth 90 Electoral College votes.

Biden also leads the polls in consistently Republican-voting Arizona (11 electoral votes).

So, if we take recent polls in these states at face value, then Trump would lose 101 of the Electoral College votes he won in 2016 and be soundly defeated.

Biden has already visited Wisconsin on the campaign trail — something Clinton failed to do in 2016. Tannen Maury/EPA

Why did state polls perform poorly in 2016?

But state polls were heavily criticised in 2016 for underestimating Trump’s support, as these charts in our research highlight.

The final poll averages in 2016 underestimated Trump’s margin over Clinton by more than five points in several swing states: North Carolina (5.3), Iowa (5.7), Minnesota (5.7), Ohio (6.9) and Wisconsin (7.2). This is calculated by taking the difference between the official election result and the average of the polls on election eve.

A review of 2016 polling by the American Association of Public Opinion Research examined a number of hypotheses about the bias of state-level polls in 2016.

Two predominant factors made the difference:

1. An unusually large number of late-deciders strongly favoured Trump

The number of “undecideds” in 2016 was more than double that in prior elections. Of these, a disproportionate number voted for Trump.

But 2020 polling to date reveals far fewer undecided voters, suggesting this source of poll error will not be as large in this year’s election.


United States Studies Centre, University of Sydney

2. Changes in voter turnout

In 2016, Trump successfully mobilised white voters who are becoming a smaller portion of the American electorate and ordinarily have low rates of voter turnout. These were largely non-urban voters and those with lower levels of education.

This year will likely see high levels of engagement from both sides — and potentially a surge in turnout unseen in decades — which could further undermine the accuracy of election polls.


United States Studies Centre, University of Sydney

Re-interpreting the 2020 polls

The latest state poll averages imply Biden will handily win the election with an Electoral College victory of 334 to 204.

But if the 2020 polls are as wrong as they were in 2016, then Biden’s current poll leads in New Hampshire, North Carolina and Wisconsin are misleading. If Biden loses these three states, the Electoral College result will be 305-233, still a comfortable Biden win.


United States Studies Centre, University of Sydney

In recent weeks, however, we have seen Biden’s poll leads in Pennsylvania and Florida be smaller than the corresponding poll error in those states from 2016.

If Trump wins these two large states (in addition to New Hampshire, North Carolina and Wisconsin), and the other 2016 results are replicated elsewhere, then he will narrowly win the election with 282 Electoral College votes.

Given the statistical range of poll errors seen in 2016 — and assuming they reoccur in 2020 — current polling implies Trump has roughly a one in three chance of winning re-election.


Read more: Winning the presidency won’t be enough: Biden needs the Senate too


What other factors will come into play?

The COVID-19 pandemic and controversies around the administration of the election could further jeopardise the validity of 2020 polling. Official statistics already show many voters are attempting to make use of voting by mail or in-person, early voting.

Access to these alternative forms of voting varies tremendously across the United States, so the political consequences are difficult to anticipate.

Trump and his Republican supporters have raised doubts about the validity and security of vote by mail. A recent opinion poll showed Democrats are much more likely to rely on vote by mail compared to Republicans (72% to 22%).

Thousands of Trump supporters take part in a caravan rally in Florida, one of the critical battleground states in the election. Cristobel Herrera-Ulashkevich/EPA

Unsurprisingly, Democrats and other groups are bringing numerous lawsuits to help ensure vote by mail remains a widely available method of voting.

It is quite likely the courts will be asked to rule on the validity of the results after the election, on the basis mail ballots have been either improperly included or excluded in official tallies.

So, will it be closer than expected?

On the one hand, this year’s election seems to have historically low levels of undecided voters, a factor that should make polls more accurate. But offsetting this is tremendous uncertainty about turnout and whose votes will be cast and counted.

All this suggests considerable caution be exercised in relying on the polls to forecast the election. These forecasts are almost surely overconfident.

The other main takeaway: Trump’s chances of re-election are likely higher than suggested by the polling we have seen to date.


The charts in this piece were initially created by Zoe Meers, formerly a data visualisation analyst at the US Studies Centre at the University of Sydney.The Conversation

Simon Jackman, Chief Executive Officer, US Studies Centre, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Simon Jackman
Simon Jackman commenced as CEO of the US Studies Centre in April 2016. Between 1996 and 2016 he was a professor of Political Science and Statistics at Stanford University. Jackman's teaching and research centres on public opinion, election campaigns, political participation, and electoral systems with special emphasis on American and Australian politics. His research has appeared in the leading journals of political science, including the American Political Science Review, the American Journal of Political Science, the Journal of Politics, Public Opinion Quarterly, Political Analysis, the British Journal of Political Science, Electoral Studies and the Australian Journal of Political Science. Jackman is the author of Bayesian Analysis for the Social Sciences (Wiley 2009), a widely used textbook on Bayesian statistical methods with an emphasis on applications in the social sciences. Since 2009, Jackman has been one of the Principal Investigators of the American National Election Studies, the world’s longest running and most authoritative survey of political behaviour and attitudes, directing this project over both the 2012 and 2016 presidential election cycles in the United States. Prior to his stewardship of ANES, Jackman directed a number of large, on-line survey projects ahead of the 2008 and 2000 US presidential election cycles. Jackman is also well known for his work on poll averaging, combining polls over the course of an election campaign to produce better predictions of election outcomes; he partnered with the Huffington Post in the American 2012 presidential election and with Guardian Australia during the 2013 Australian election, supplying exclusive analysis and commentary on pre-election polling. Jackman is also a frequent commentator on American politics in Australia media, regularly appearing on the ABC’s The World Today, News 24 and the 7.30 Report. Jackman’s current research projects focus on the opportunities and challenges of web-based survey research, the political and scientific consequences of under-representing unlisted or hard-to-reach populations in social research, predictive models of political behaviour, and methods for large scale, automated coding and analysis of political speech. Jackman was born and raised in Brisbane, and graduated with first class Honours in Government from the University of Queensland. Jackman earned his doctorate at the University of Rochester and Princeton University. His first academic appointment was at the University of Chicago, followed by a Visiting Fellowship at Australian National University, prior to taking up his appointment at Stanford. Jackman was a Visiting Professor at the US Studies Centre from 2009 until he commenced his role as CEO in 2016. In 2013 Jackman was elected to the American Academy of Arts and Sciences. He is a past president and Fellow of the Society for Political Methodology. Along with his wife and two children, he is a citizen of both Australian and the United States of America.

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