Berniesanders

Democratic Debate is on: Hillary Clinton, Bernie Sanders in the spotlight; Trump's Twitter show calls it 'boring'

The surprise rivalry between front-runner Hillary Rodham Clinton and insurgent Bernie Sanders will be at the forefront as Democrats take the stage Tuesday in Las Vegas for the party's first debate of the 2016 presidential campaign.

Watch: Who is Bernie Sanders, what's his pitch?

The Republican presidential contest has been aflutter for months, but now it's time for the Democrats to spread their wings before a big national audience. Their first debate is Tuesday night on CNN, 8:30 pm Eastern Time. Here is a guide to the top candidates.