Cruz: Active on Facebook and Twitter, much content is pumped out by staff. Tweeted Google map directions to the Mexican border to help Obama find it — a poke at the president's decision not to visit the scene of the child-migrant crisis during a Texas find-raising trip in July. But the Texas senator himself has been no closer to the border than 150-plus miles since the crisis began.
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 last year that he'd attracted more than 1 million likes for his Facebook page, where he listed 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.
Rubio: Aggressive, with large followings, appears to make personal use of Twitter more than staff-generated Facebook. Takes lots of shots at the health law. On Facebook, lists "Pulp Fiction" movie and "The Tudors" historical fiction TV series among favorites.
Ryan: King of Facebook among potential rivals in both parties, with nearly 4.9 million likes. Seeks $10 donations for "Team Ryan" bumper stickers for his PAC and kisses a fish. Posts photo of Obama with his feet up on Oval Office desk. Commanding presence on Twitter, too, via an account associated with his PAC and another as congressman.
Santorum: Active on Twitter and Facebook.
Walker: Posts vigorously on Facebook and on his Twitter accounts. Many exclamation points. "Glad USDA is keeping cranberries on school menus. I drink several bottles of cranberry juice each day!" Promotes policy achievements and his TV appearances, reflects on sports, pokes Obama.
Associated Press writers Ken Thomas and Josh Lederman in Washington; Brian Witte in Annapolis, Maryland; Tom Beaumont in Des Moines, Iowa; Steve Peoples in Boston; Michael Virtanen in Albany, New York; Will Weissert in Austin, Texas; Melinda Deslatte in Baton Rouge, Louisiana; and Erik Schelzig in Nashville, Tennessee, contributed to this report.