Will Joe Biden slip again or succeed: what to watch for in tonight's debate

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Tonight is a critical test for Joe Biden after his weak performance in the first round. Showing renewed strength in new national polls, will he be tougher tonight, or falter again. Joining Andrea Mitchell to break it all down is NBC White House correspondent Kristen Welker, NBC senior political editor Mark Murray, and host of 'Hardball' here on MSNBC, Chris Matthews.