The race is narrowing. Today, Republican Rand Paul said he's bowing out of the 2016 presidential contest. He follows fellow Republican Mike Huckabee and Democrat Martin O'Malley. They both called it quits – or 'suspended their campaigns' as politicians put it – shortly after the results of the Iowa caucases came in Monday night.

This brings up a big question: if you're dropping out, how and when should you do it?

If history is any guide, making smart choices when throwing in the towel can mean a lot to a candidate's future.

For more we turn to Matt Latimer, contributing editor at Politico. He's also a former speech writer for George W. Bush.