Who will challenge Donald Trump in 2020?

The 2020 Democratic primary election is already one of the most hotly contested in history, with over 20 candidates vying to lead the party. John Prideaux, our US editor, takes a look at the front-runners. Click here to subscribe to The Economist on YouTube: https://econ.st/2xvTKdy Read more here: https://econ.st/2X2ZdzG For more from Economist Films visit: http://films.economist.com/ Check out The Economist’s full video catalogue: http://econ.st/20IehQk Like The Economist on Facebook: https://www.facebook.com/TheEconomist/ Follow The Economist on Twitter: https://twitter.com/theeconomist Follow us on Instagram: https://www.instagram.com/theeconomist/ Follow us on Medium: https://medium.com/@the_economist