A big day in presidential politics: Texas Gov. Rick Perry dropped out of the race. Certified results from the Iowa caucuses show former Pennsylvania Sen. Rick Santorum finished ahead of former Massachusetts Gov. Mitt Romney, but party officials are calling it a tie. And Newt Gingrich's second wife sat down with ABC News for an interview about their marriage and messy divorce. All this comes on the same day the four remaining candidates gather in Charleston, S.C. for a debate. Robert Siegel discusses it all with NPR's Mara Liasson in Charleston.