The calculus for the 2016 race for the White House has shifted after 2012 Republican presidential nominee Mitt Romney decided not to run again. Here are a few of the possible contenders:
Republicans
Jeb Bush: Is the country ready for a third Bush president? The former Florida governor, brother of one president and son of another, has been testing the waters of a White House bid. But his moderate positions on immigration, education and other issues mean Bush, 61, is not popular among many conservatives. His Right to Rise political action committee hired a strategist who in 2012 ran Romney's campaign in Iowa, one of the first states with presidential nominating contests.