The largest Democratic Debate in U.S. History will take place in Westerville Ohio tonight.

Democrats are confronting a rapidly shifting political landscape. Former Vice-President Joe Biden faces allegations of wrongdoing regarding payments to officials in the Ukraine. His front-runner status is also under threat from Massachusetts Sen. Elizabeth Warren, who is also fending off new questions about her biography. Adding to the drama, Bernie Sanders is recovering from a heart attack that raised questions about his ability to withstand a campaign.

Democratic National Committee Chairman Tom Perez explains why Westerville and Otterbein University was selected.