Viable challenges to Clinton campaign as 2016 race narrows
Wisconsin Gov. Scott Walker officially joins the presidential race a week from Monday, and former Virginia Senator and Navy Secretary Jim Webb became the fifth contender for the Democratic nomination Thursday. Democratic Vermont Sen. Bernie Sanders is also surging after drawing a crowd of 10,000 this week in Wisconsin. Washington Post columnist Dana Milbank joins "CBS This Morning" from Washington to discuss the latest contenders in the 2016 race to the White House.