Bernie Sanders represents the polar opposite of the American political spectrum from the man he looks to defeat in 2020, US President Donald Trump.
After Mr Sanders announced his bid to seek the Democratic nomination — and a chance to unseat Mr Trump from the White House — the philosphical and political battle lines for next year's US election are taking shape.
Also announcing bids have been Democratic Senators Elizabeth Warren, Kamala Harris, Kirsten Gillibrand and Cory Booker. The Democratic Party is now split between the new generation of what is, in American political terms, radical progressives, and those who believe only a traditional centrist Democrat nominee can win the White House.
In the latest edition of Sightline, Tim Marshall breaks down what Mr Sanders' bid to run for president means for the Democratic Party and US politics.
Watch above.
