CBS News poll: Donald Trump retakes lead in Iowa

Iowa caucuses are one week from Monday, and the latest CBS News Battleground Tracker shows Donald Trump is back in the lead there. The survey finds Trump is five points ahead of Ted Cruz, who led in the same poll a month ago. Our New Hampshire Battleground Tracker finds Trump holds an 18-point lead, with Cruz, Marco Rubio and John Kasich fighting for second place. Major Garrett reports.