Bernie Sanders, the plain-speaking and occasionally dishevelled socialist senator from Vermont who has become the unlikely Democratic primary frontrunner in some key early states, will appear on the cover of this week's Time magazine.

Over recent months Senator Sanders has campaigned around the country to increasing popularity, focusing laser-like on the issue that matters most to many Democrats – economic inequality.

Bernie Sanders on the cover of Time magazine.

Meanwhile the party's frontrunner, Hillary Clinton, has spent much of her time defending herself from allegations that she was dishonest and paranoid by breaking with protocol and using her own internet server and email system rather than the State Department's system while serving as secretary of state.