2020 elections - three weeks out.

 Four years ago, I found it inconceivable that Trump would win the presidency.  Much of that was focused on Clinton winning Pennsylvania, Michigan and Wisconsin, which had been solidly Democratic for the prior twenty years.  

Trump's ability to make those inroads, along with capturing Florida, gave him the path to victory.  In 2016, many pollsters undercounted the enthusiasm of Trump voters, leading to heavier Republican turnout, and the real lack of enthusiasm among potential Clinton voters.  There was a marked drop off in minority democratic votes, not surprising given the record turnouts that Obama motivated.

This year, 2020, once again seems poised for a Democratic win.  Based on polling three weeks before the election, we see a prediction for a Biden landslide.

In this scenario, Trump loses Florida, Arizona, Georgia, North Carolina, Ohio, Iowa, Wisconsin, Michigan, and Pennsylvania - all states that he carried in 2016.  This map, I think, is the best case scenario for the Democrats in 2020.

There is an expectation that Trump supporters will once again exceed polling expectations.  There is an undercount, perhaps due to many Trump supporters not participating honestly in polls.  There is also the repeated risk of undercounting pro-Trump turnout due to Trump enthusiasm.

That said, at the risk of being wrong again, I don't think that will be as stark in 2020.  While Biden supporters are not particularly enthusiastic for Biden, they do not have the same level of hostility as they did to the Clinton campaign in 2016. Many liberal voters also regret sitting out 2016 and are not willing to make that mistake again.

Even with a bump for Trump enthusiasm, it is heard to see a path to Trump victory.  A map giving Trump every state where consensus polls show him within 5% of Biden still give a slim electoral victory to Biden.

In this scenario, Biden wins back the critical states of Wisconsin, Michigan, and Pennsylvania, while holding on to every state that Clinton won.  If Trump cannot turn around a 6% or 7% polling deficit in those three states, it is difficult to imagine a path to reelection.