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To be front and center at tonights republican presidential debate. joining me now to break down other issues to watch for at the showdown in las vegas, host and correspondent steve kornacki. steve? >> kate, obviously, we can expect national security as you say to be a major issue, major point of emphasis tonight, but also, the question is, how are the candidates going to use that issue and others to draw contrast, try to draw distinctions with each other? we thought wed give you a guide do a few...