New Jersey Gov. Chris Christie
The governor was begged by many Republicans to run in 2012, but ultimately refused the bid. Christie is blunt and can be partisan, but has worked effectively with a Democratic Legislature and has been praised for his response to Hurricane Sandy. His keynote speech at the Republican National Convention promoted himself more than Mitt Romney.
Wisconsin Rep. Paul Ryan
Despite losing the 2012 election as Romney's running mate, Ryan kept his seat in the House of Representatives, and remains on the radar for running in 2016. As the chairman of the House Budget Committee, Ryan is considered a top Republican fiscal expert.
Florida Sen. Marco Rubio
The freshman senator is considered an extremely attractive presidential hopeful with foreign policy experience, including serving on the Senate Select Committee on Intelligence and the Committee on Foreign Relations. The Cuban-American is a leading Hispanic conservative who appeals to Republicans reeling from a disastrous showing in the Latino vote.
Virginia Gov. Bob McDonnell
The governor, known for being the chairman of the Republican Governors Association, is considered effective handling his Legislature and is one of the few hopefuls with military experience.