It's the moment everybody's been waiting for: Tonight's Democratic debate in Houston will be the first face-off on the primary stage between Elizabeth Warren and Joe Biden.
Why it matters: They appeal to totally different wings in the Democratic Party. Warren's momentum has moved her to the No. 2 spot in national polls and narrowed Biden's lead. Tonight's matchup has the potential to be an even bigger split-screen moment than when Kamala Harris took on Biden at the first debate — and Biden's team knows it.