Next Democratic debate will officially be a Biden-Sanders face-off

It's time for the main event... before the actual main event.The Democratic National Committee announced the rules for its March 15 debate on Friday, saying only candidates with more than 20 percent of the delegates doled out so far will appear onstage. That ensures only former Vice President Joe Biden and Sen. Bernie Sanders (I-Vt.) will get to face off, and removes Rep. Tulsi Gabbard (D-Hawaii) and her one delegate from the contest.Biden, Gabbard, and Sanders are the only candidates left in th