New Jersey Gov. Chris Christie, a Republican, campaigns for GOP presidential hopeful Mitt Romney in Manchester, N.H., on Nov. 9. Surrogates such as Mr. Christie have been scarce thus far this election cycle, partly because voters want to meet the candidates themselves. (Associated Press)
To become the GOP standard-bearer, Mr. Santorum must leapfrog past rivals (from left) Mitt Romney, Herman Cain and Newt Gingrich. (Associated Press)
Republican presidential candidate Mitt Romney, with Sen. John Thune of South Dakota, speaks Wednesday to workers at Nationwide Insurance Co. in Des Moines, Iowa. Mr. Romney is using a tough stance against illegal immigration to separate himself from his rivals for the nomination. (Associated Press)
Republican presidential candidate Rep. Ron Paul of Texas speaks as Texas Gov. Rick Perry and former Massachusetts Gov. Mitt Romney listen at a Republican presidential debate in Washington on Nov. 22, 2011. (Associated Press)
Republican presidential candidates from left, former Massachusetts Gov. Mitt Romney shakes hands with businessman Herman Cain, as former House Speaker Newt Gingrich stands on stage before a Republican presidential debate in Washington, Tuesday, Nov. 22, 2011. (AP Photo/Evan Vucci)
**FILE** Republican presidential candidates (from left) former Utah Gov. Jon Huntsman, Rep. Michele Bachmann of Minnesota, Rep. Ron Paul of Texas, businessman Herman Cain, Former Massachusetts Gov. Mitt Romney, former House Speaker Newt Gingrich, Texas Gov. Rick Perry, and former Pennsylvania Sen. Rick Santorum prepare Nov. 12, 2011, before the CBS News/National Journal foreign policy debate in Spartanburg, S.C. (Associated Press)
Former Massachusetts Gov. Mitt Romney, a Republican presidential candidate, speaks to supporters outside City Hall in Nashua, N.H., on Sunday. Sen. Kelly Ayotte (left) of New Hampshire listens. Mrs. Ayotte endorsed Mr. Romney. (Associated Press)
Republican presidential candidate Mitt Romney, a former Massachusetts governor, has said the United Nations too often becomes a forum for tyrants when it should promote democracy and human rights. (Associated Press)
**FILE** Republican presidential candidate Newt Gingrich (left) speaks Nov. 12, 2011, during the CBS News/National Journal foreign policy debate at the Benjamin Johnson Arena in Spartanburg, S.C., as fellow candidate and former Mass. Gov. Mitt Romney listens. (Associated Press)
