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First PollyVote forecast predicts a tight race


The first PollyVote forecast for the 2020 U.S. presidential election, published in late April, predicts a tight race for the national popular vote.

As of April 26, the combined PollyVote predicts incumbent President Donald Trump to gain 49.1% of the popular two-party vote, compared to 50.9% for former Vice President Joe Biden, with an 80%-uncertainty interval of +/-2.7 percentage points.

Based on these numbers, the estimated probability for Biden to win the popular vote is 67%. In other words, the PollyVote predicts Biden to win the popular vote two out of three times, whereas Trump is predicted to win one out of three times.

Table 1 shows the point forecasts from the PollyVote and the components, for which data are currently available. Forecasts based on both polls (intentions) and expectations see Biden ahead, whereas model-based forecasts and naive forecasts see a very small advantage for Trump.

Intentions (polls) (RCP average)46.753.3
– Prediction markets (7-day IEM average)49.051.0
Expert judgment47.752.3
– Retrospective (1 model, DeSart)54.445.6
– Hybrid (1 model, Fair)47.152.9
Naive forecast (2 models, electoral cycle and 50/50)50.649.4
Table 1: The PollyVote and its components, forecasts from April 26, 2020

It should be noted that available data that go into the PollyVote are still limited. The poll-based component is merely based on the RCP average, prediction markets rely on the small-scale Iowa Electronic Markets, and there is only one model forecast each in the retrospective model and the hybrid model category.

Loyal followers of the PollyVote will note that the PollyVote structure has changed compared to previous elections. We will explain our rationale for this adjustment in a future post. Stay tuned.

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