Who is the best Democratic candidate for 2020?

College Democrat view

Although it has been clichéd into oblivion, Trump loses when Democratic turnout peaks.  

Democratic voters, especially older ones, tend to see voting as somewhat of a civic responsibility, which is why voter turnout among older voters is always higher than younger voters. It is likely that the vast majority of potential Democratic voters are going to vote for the nominee. So if the majority of the Democratic coalition is going to support the nominee regardless of who it is, the way to win is to make sure the Democratic candidate can energize non-voters and get those people, along with younger voters, to the polls.  

Ask yourself: which candidate in the Democratic primary has the most enthusiastic voters and the most support among young people? The answer is clear: Bernie Sanders.
Sanders constantly polls miles above every other candidate, including Trump, when it comes to younger voters. It is always very difficult to turn out young voters, as they are not typically reliable voters, but in my view Sanders has the most potential to turn out the youngest people. Furthermore, Sanders constantly over-performs in polls in the Midwest, famously winning Michigan in the 2016 Democratic primary, out-performing a 15% deficit. The two most important blocks to turn out are young voters and midwestern voters, each very much in Sanders’ wheelhouse.
Despite what conventional wisdom may lead you to believe, Sanders also has the most potential to pull disillusioned Trump supporters. Sanders and Trump are both populist candidates. Acknowledging that truth and acknowledging there are systemic reasons why blue collar Midwestern voters thought flipping the system on its head was a better idea than electing the most qualified candidate in U.S. history, makes the crossover appeal between Trump and Sanders understandable.  
Voters in the rust belt, which will deliver this election, want an anti-establishment candidate to actually try to improve their lives. Trump lied about his populism. Up against a real populist who constantly polls well in the Midwest, among young people and against Trump, Bernie Sanders is the only real chance to make Trump a one term president.