(CNN) President Donald Trump has seen his approval ratings tilt upward because of his response to the coronavirus pandemic. Unfortunately, the US economy is in a tailspin because of that same pandemic. A record of nearly 10 million Americans have filed unemployment insurance claims the past two weeks and the country had a net loss of 700,000 jobs in the month of March. If history holds, this downward swing in the economy could wipe out any gains Trump has made in his popularity and put his reelection bid in great peril.

The relationship between the state of the economy and a president's fortunes is one of the clearest in political science. We can see this if we look at raw economic data (such as jobs or gross domestic product ), or when we simply ask voters about how they think the economy is doing.

Election forecasts based solely on current and projected trends for job growth are bad enough that if history repeats itself, Trump will lose in a blowout unless there's a very strong upswing later in the year. Forecasted changes in GDP are so dire that they are literally off the scale for at least one model (i.e. the model could predict Trump getting a negative number of electoral votes).

With a potential black swan event in the making, it might be safest to stick to polling around the economy to understand its potential impact on 2020. The question of "is the economy getting better, worse or staying the same?" has been quite predictive in the final polls of every incumbent election since 1976. When incumbent Jimmy Carter got blown out in 1980, voters by a 32 point margin said the economy was getting worse than better. When incumbent Ronald Reagan was winning easily four years later, voters by a 21 point margin said the economy was getting better than worse.

Overall, incumbents have lost every election in which 15 points or more of voters said the economy was getting worse than getting better. Meanwhile, the incumbent has won every election when that was not the case.

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