Ryan: His Prosperity Action PAC.
Santorum: Keeps in touch with chief supporters of his winning 2012 Iowa caucus campaign, giving him a leg up on a campaign organization in that state.
Walker: Consults with top Republican governor strategists such as Phil Musser and Nick Ayers.
GET WITH IT ON SOCIAL MEDIA: A must for spreading ideas, poking competitors, raising money, organizing events and showing a personal side, though often a very canned version.
Biden: Launched Instagram account in April. Not active on Facebook, occasional contributor to his office's vigorous Twitter account.
Clinton: More than 1 million followers on Twitter, her preferred social media outlet.
Cuomo: Few if any personal tweets; Facebook also generated primarily by staff.
O'Malley: On Twitter, standard governor's fare but promotes rare appearances by his Celtic rock band, O'Malley's March, for which he sings and plays guitar, banjo and tin whistle. On Facebook, his PAC-generated page is more active than official governor's account.
Bush: Tweets and posts many Wall Street Journal stories, education thoughts and some Bush family doings.
Christie: More engaged in Twitter ("It was great to be able to visit with the owners of Rossi's Rent-A-Rama in Ortley today.") than Facebook.
Cruz: Active on Facebook and Twitter, much content is pumped out by staff.
Jindal: Active on Twitter and on Facebook, where he lists among favorite books, "John Henry Newman: A Biography," about recently canonized British cardinal and sage. Also favors James Bond movies.
Paul: Aggressive. Bragged on Twitter in June that he'd attracted more than 1 million likes for his Facebook page, where he lists his own books as his favorites.
Perry: Active. One popular tweet was accidental — from his pocket, he said — and consisted of "I." Followers jumped in to complete his sentence. One offered: "I ... really like Obamacare." (He doesn't.) Facebook appears staff-generated.