Shields and Ponnuru on Christie endorsing Trump, GOP debate

Judy Woodruff joins syndicated columnist Mark Shields and Ramesh Ponnuru of the National Review to discuss the week in politics, including Gov. Chris Christie’s endorsement of Donald Trump, Sen. Ted Cruz and Sen. Marco Rubio’s chances of derailing a Trump nomination, Sen. Bernie Sanders’ decision to leave South Carolina before the primary and President Obama’s Supreme Court standoff.