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In 2016, Hillary Clinton went into Election Day leading Donald Trump in the RealClearPolitics poll average in Pennsylvania (+1.9 percentage points), Michigan (+3.4 points), and Wisconsin (+6.5 points). Trump would go on to win all three states by less than one percentage point—a polling error that shocked the world.
This time around, Democratic nominee Joe Biden also leads poll averages in Michigan (+8.1 points), Pennsylvania (+5.3 points), and Wisconsin (+4.6 points). But it doesn’t stop there. In all, Biden is leading in seven states Trump won four years ago, including Arizona (+2.4 points), Florida (+1.5 points), Iowa (+0.8 points), and North Carolina (+1.2 points). Trump holds narrow leads in Georgia (0.4 points), Ohio (0.6 points), and Texas (2.6 points).
But what’s the result if the polling error in 2020 is identical to that in 2016? To find out, Fortune used RealClearPolitics 2016 poll averages to calculate polling errors in 14 battleground states. Then we applied those 2016 state polling errors to states’ 2020 RealClearPolitics poll averages.
The result? Biden would win in a 342 electoral vote landslide.* In that scenario, he’d pull out narrow victories in four states Trump won five years ago, including Arizona, Florida, Michigan, Pennsylvania, and Texas. Trump would take Iowa, Georgia, North Carolina, Ohio, and Wisconsin—which had a 7.2 point polling error in 2016.
How is it possible for Biden to take Texas, yet at the same time Trump snags Wisconsin? While in 2016, Trump significantly outperformed his Midwest polls, he actually fared worse in Southwest states like Arizona, Nevada, and Texas. Trump led Clinton by a poll average of 0.8 points in Nevada—a state Clinton would win by 2.4 points. And in 2016, Trump’s 12.0 point poll average lead in Texas only translated to a 9.0 point win. If you apply that 3.0 polling error to Trump’s current 2.6 point poll average lead in Texas, it would translate into a 0.4 point Biden win in the Lone Star State.
But this scenario—despite the massive electoral vote tally—wouldn’t be the Biden runaway it appears. Applying a 2016 polling average, Biden would narrowly win Florida (0.5 points), Minnesota (1.3 points), and Texas (0.4 points). Those states account for 77 electoral votes. It takes 270 to win.
Keep in mind that while state polling was off by a lot four years ago, national polling was fairly accurate: Clinton had a national 3.2 point RealClearPolitics poll average lead, and she finished with a 2.1 point popular vote win. This time, nationally Biden has a 8.3 point poll average lead. If Biden beats Trump in the popular vote by 6 percentage points, his chances of winning the election are 99%, according to FiveThirtyEight editor-in-chief Nate Silver. But if it’s only a popular vote win of 1 to 2 percentage points, Biden’s chance of an electoral college win drops to 22%.
As of Monday, FiveThirtyEight forecast the odds of Biden winning at 88%, while The Economist forecast the Democratic nominee having a 94% chance of winning the electoral college.
* This scenario includes Trump winning Maine’s second congressional district and Nebraska’s second congressional district, which FiveThirtyEight rates as being to the political right of Michigan, Pennsylvania, and Wisconsin.