Senator Marco Rubio, a Republican from Florida and 2016 presidential candidate, pauses while speaking during the American Conservative Unions Conservative Political Action Conference (CPAC) meeting in National Harbor, Maryland, U.S., on Saturday, March 5, 2016. After 10 debates spent attacking each other, underdog Republicans finally focused virtually all their collective fire this week on Donald Trump, the Republican front-runner who was savaged by the last Republican nominee just hours earlier in a dramatic broadside. Photographer: Andrew Harrer/Bloomberg via Getty Images