After the results of the Super Tuesday primaries in the United States, two candidates have emerged as front-runners in the battle for the Democratic Party's presidential nomination - Joe Biden and Bernie Sanders. But which vision for the future of the party will be the one more likely to deliver electoral success across the nation? One that aims to reach out to swing voters and Republicans, or one that energises the base of the party and attempts to bring new people to the polls? Is history a good indicator of how each candidate would perform in the general election, or has politics in America changed beyond recognition? Can Democrats beat President Trump - and if so, how?