In the weeks leading up to the 2020 general election, different pollsters told very different stories about who would win. Some managed to get pretty close to the actual result: a 4.5 percentage point win for Joe Biden. But some polls showed a landslide victory for Biden, and others showed a win for Donald Trump. So why did some pollsters get the outcome so right while others got it so wrong? In this episode of Polling 101, FiveThirtyEight database journalist Dhrumil Mehta (a.k.a. Professor Polls) walks us through the update of FiveThirtyEight’s Pollster Ratings and explains what makes a good pollster.