GOP candidates on the trail

AP120313143063(1).jpg — AP Photo/Evan Vucci

Republican presidential candidate, former Massachusetts Gov. Mitt Romney hands out cookies before departing on a flight, March 13, 2012, in St. Louis, Mo.

Rick Santorum

Dusty Compton,AP Photo/The Tuscaloosa News

Republican presidential candidate Rick Santorum greets supporters at the Original Dreamland BBQ in Tuscaloosa, Ala., March 12, 2012.

Newt Gingrich

Republican presidential candidate Newt Gingrich thanks supporters at an election night party with his wife, Callista March 13, 2012, in Birmingham, Ala.

Ron Paul

Republican presidential candidate, Rep. Ron Paul, R-Texas speaks at the University of Missouri, March 15, 2012, in Columbia, Mo.

Mitt Romney

Gov. Phil Bryant, R-Miss., right, watches as Republican presidential candidate Mitt Romney speaks during a campaign stop at the Port of Pascagoula on, March 8, 2012, in Pascagoula, Miss.

Rick Santorum

Republican presidential candidate Rick Santorum talks during a rally on March 9, 2012, in Topeka, Kan.

Newt Gingrich

The tour bus of Republican presidential candidate former House Speaker Newt Gingrich waits for his return outside a campaign event, March 13, 2012, in Vestavia Hills, Ala.

Ron Paul

Republican presidential candidate Ron Paul acknowledges supporters as his wife Carol looks on during a primary night party Feb. 28, 2012, in Springfield, Va.

Mitt Romney

Republican presidential candidate Mitt Romney greets supporters who braved the rain during a campaign stop at the Whistle Stop Cafe, March 12, 2012, in Mobile, Ala.

Mitt Romney

Republican presidential candidate Mitt Romney, left, laughs with the lead singer of the band Alabama, Randy Owen, during a campaign stop at Thompson Tractor on March 9, 2012, in Birmingham, Ala.

Rick Santorum

Republican presidential candidate Rick Santorum meets with some campaigners on March 4, 2012, at a BBQ in Memphis, Tenn.

Mitt Romney

Republican presidential candidate, former Massachusetts Gov. Mitt Romney, speaks during a campaign stop in San Juan, Puerto Rico, March 16, 2012.

Rick Santorum

Karen Santorum, right, helps prepare her husband, Republican presidential candidate Rick Santorum, for a live interview following a rally, March 12, 2012, in Montgomery, Ala.

Ron Paul

Republican presidential candidate Ron Paul walks to his vehicle after holding a town hall style campaign event about "Solving Detroit's Crises" on Feb. 27, 2012, in Detroit, Mich.

Rick Santorum

Republican presidential candidate Rick Santorum gives a speech for supporters gathered during a "Rally for Rick" at Atlantic Aviation on March 1, 2012, in Atlanta, Ga.

Rick Santorum

Republican presidential candidate, former Pennsylvania Sen. Rick Santorum, right, waves at supporters following a campaign rally in Old San Juan, Puerto Rico, March 15, 2012.

Newt Gingrich

Republican presidential candidate Newt Gingrich listens while participating in the Rick & Bubba radio show, March 13, 2012, in Vestavia, Ala.

Newt Gingrich

Republican presidential candidate Newt Gingrich is hugged by Helen Smalley (R) and Betty Weeks (L) after speaking to the Vestavia Hills Chamber of Commerce at the Vestavia Hills Country Club March 13, 2012, in Birmingham, Ala.

Rick Santorum

Republican presidential candidate, former Sen. Rick Santorum addresses supporters after winning the both Alabama and Mississippi primaries on March 13, 2012 in Lafayette, Louisiana.

Mitt Romney

Republican presidential candidate, Mitt Romney, Mississippi Gov. Phil Bryant, center, and others, bow their heads during a prayer prior to Romney speaking at the Mississippi Farmers Market in Jackson, Miss., March 9, 2012.

Newt Gingrich

Republican presidential candidate Newt Gingrich campaigns at the Wiregrass Museum of Art on March 10, 2012, in Dothan, Ala.

Ron Paul

Supporters of Republican presidential candidate and Rep. Ron Paul, R-Texas, listen during a primary night party on Feb. 28, 2012, in Springfield, Va.

Mitt Romney

Republican presidential candidate, former Massachusetts Gov. Mitt Romney greets supporters during an Illinois GOP primary victory party at the Renaissance Schaumburg Convention Center Hotel, March 20, 2012 in Schaumburg, Ill.

Ron Paul

Republican presidential candidate Ron Paul as he leaves in his vehicle from a town hall style campaign event about "Solving Detroit's Crises" on Feb. 27, 2012, in Detroit, Mich.

Mitt Romney

Republican presidential candidate, former Massachusetts Gov. Mitt Romney greets people during a campaign stop at a Cousins Subs fast food restaurant, in Waukesha, Wis., April 3, 2012.

Rick Santorum

Republican presidential candidate, former Pennsylvania Sen. Rick Santorum, right, is joined by his daughter Sarah Maria during a news conference in Green Bay, Wis., March 24, 2012.

Rick Santorum

Republican presidential candidate, former Sen. Rick Santorum delivers remarks in front of the Supreme Court on the first day of oral arguments in the Patient Protection and Affordable Care Act March 26, 2012 in Washington, D.C.

Newt Gingrich

Republican presidential candidate, former House Speaker Newt Gingrich is applauded by his wife Callista as he address people gathered at a local restaurant in New Orleans, Gingrich is standing in front of a mural of downtown New Orleans, March 16, 2012.

Newt Gingrich

Republican presidential candidate, former House Speaker Newt Gingrich talks to members of the Hispanic community at a private residence at Oakland Plantation Estates in Kenner, La., March 23, 2012.

Ron Paul

Republican Presidential hopeful Rep. Ron Paul autographs a supporter's book during a town hall meeting at the University of Maryland on March 28, 2012 in College Park, Md.

Ron Paul

Republican Presidential hopeful U.S. Rep. Ron Paul speaks during a town hall meeting at the University of Maryland on March 28, 2012 in College Park, Md.