The media’s coverage of the 2016 presidential campaign has come to be criticized for operating under three key assumptions: that Hillary Clinton was certain to be the Democratic nominee, that Donald Trump was unlikely to be the Republican nominee, and that once Clinton and Trump had become their party’s nominees, she would win. With voting for 2020 set to begin in Iowa on Monday, “The Daily” sat down with Dean Baquet, the executive editor of The New York Times, to discuss the lessons he — and the organization — learned from 2016. For more information on today’s episode, visit nytimes.com/thedaily.  Background reading: This is our guide to the 2020 election.We’ve sent reporters to every corner of the country and told them not to make any assumptions in this election cycle. Here are some of the most in-depth stories we’ve told in an effort to help the country understand itself.As part of a new approach to election coverage, The Times’s editorial board has re-examined how — and why — it makes presidential endorsements.