The four remaining GOP presidential candidates are all on Twitter, tweeting mostly press releases rather than personal anecdotes or responses.

Mitt Romney’s Twitter account, @MittRomney, has been known to tweet the odd hand-held video and occasional photos of the candidate eating Subway sandwiches or boarding a Southwest airplane. Newt Gingrich, @NewtGingrich, typically tweets videos, policy statements and the location of his campaign events, similar to Rick Santorum, @RickSantorum.

On Monday, Santorum used Twitter to thank Sarah Palin, Rick Perry, Romney “and the many others who prayed for Bella's recovery” during the health crisis of Santorum’s baby daughter Bella, which briefly took him off the campaign trail.

Although Ron Paul’s grassroots fans tend to be social media enthusiasts, the candidate uses Twitter infrequently. This month, he notably used Twitter to reveal that his son, Sen. Rand PaulRand PaulGOP healthcare plans push health savings account expansion Congress must reform civil asset forfeiture laws ­ObamaCare fix hinges on Medicaid clash in Senate MORE (R-Ky.), was “detained by TSA for refusing full body pat-down after anomaly in body scanner in Nashville.” The issue subsequently became a statement by the campaign condemning the Transportation Security Administration.

Independent and struggling candidates tend to use Twitter more aggressively in their campaign outreach. Libertarian candidate Gary Johnson, @GovGaryJohnson, and Republican Buddy Roemer, @BuddyRoemer, are prolific tweeters, as was Rep. Thaddeus McCotter (R-Mich.) before he dropped his GOP bid for the White House in September. McCotter would often tweet his alternative activities during GOP debates when he was not invited to participate.