Bernie Sanders is a socialist and a grump. But is he also a future US president?

Some 20,000 people recently turned out to hear Sanders speak - the sort of crowd Barack Obama would have been proud of in 2008. He is, it seems, an increasingly viable contender for the Democratic presidential nomination.

Sanders has spent the last forty years attacking inequality and he is known for giving loud and impassioned speeches. But he can also be prickly with the media and he doesn't do small talk.

So could Bernie Sanders, the self-styled socialist and "grumpy old guy", beat Hillary Clinton - and the Republicans - to become the next President of the United States? Chris Bowlby reports.

Producers: Keith Moore and Ben Crighton

The song "Feel the Bern", used in this programme, was performed by Tony Tig and produced Corbett.