On the trail in Iowa

Republican presidential candidate, former Pennsylvania Sen. Rick Santorum is surrounded by media as he orders food at Buffalo Wild Wings during a campaign stop on Dec. 30, 2011 in Ames, Iowa.

Mitt Romney

Republican presidential candidate, former Massachusetts Gov. Mitt Romney speaks during a rally at Missouri Valley Steel in Sioux City, Iowa, Dec. 16, 2011.

Michelle Bachmann

Republican presidential candidate, Rep. Michele Bachmann, R-Minn. campaigns at Sneakers Eatery and Pub in Fort Dodge, Iowa, Dec. 30, 2011.

Newt Gingrich

Republican presidential candidate, former House Speaker Newt Gingrich speaks to reporters during a campaign stop at the Southbridge Mall in Mason City, Iowa, Wednesday, Dec. 28, 2011.

Rick Perry

Republican presidential candidate Texas Gov. Rick Perry speaks during a campaign stop at The Gigglin' Goat in Boone, Iowa, Dec. 31, 2011.

Ron Paul

Supporters of Republican presidential candidate, Rep. Ron Paul, R-Texas, cheer as he campaigns at the Iowa State Fair Grounds in Des Moines, Iowa, Wednesday, Dec. 28, 2011. (AP Photo/Charles Dharapak)

Michelle Bachmann

Republican presidential candidate, Rep. Michele Bachmann, R-Minn., sits on a motorcycle during a campaign stop at the National Motorcycle Museum in Anamosa, Iowa, Dec. 22, 2011. (

Rick Santorum

Republican presidential candidate former Pennsylvania Sen. Rick Santorum walks among empty recliners during a campaign stop at USA Furniture and Bedding, Wednesday, Dec. 28, 2011, in Dubuque, Iowa.

Newt Gingrich

Republican presidential candidate, former House Speaker Newt Gingrich greets local residents after speaking at the Willow Ridge Golf Course, Dec. 15, 2011, in Fort Dodge, Iowa.

GOP Debate

Republican presidential candidates from left, former Pennsylvania Sen. Rick Santorum, Texas Gov. Rick Perry, former Massachusetts Gov. Mitt Romney, former House Speaker Newt Gingrich, Rep. Ron Paul, R-Texas, Rep. Michele Bachmann, R-Minn., and former Utah Gov. Jon Huntsman arrive for a Republican presidential debate in Sioux City, Iowa, Dec. 15, 2011.

Mitt Romney and Chris Christie

Republican presidential candidate, former Massachusetts Gov. Mitt Romney listens at right as New Jersey Gov. Chris Christie speaks during a campaign appearance at a Hy-Vee grocery store, Dec. 30, 2011, in West Des Moines, Iowa.

Ron Paul

Rep. Ron Paul, R-Texas, campaigns at the Cass County Community Center in Atlantic, Iowa, Dec. 29, 2011.

Rick Perry

Republican presidential candidate, Texas Gov. Rick Perry greets supporters after a campaign stop at the Fainting Goat in Waverly, Iowa, Dec. 30, 2011. Republican presidential candidates are largely shifting from persuading voters to mobilizing them for Tuesday's caucuses.

Rick Perry

Republican presidential candidate, Texas Gov. Rick Perry speaks during a campaign stop at the Westside Conservative Club breakfast, Dec. 28, 2011, in Urbandale, Iowa.

Ron Paul

Republican Presidential hopeful Texas Rep. Ron Paul answers a question during a campaign event, Nov. 18, 2011 at the Lawrence Community Center in Anamosa, Iowa.

Mitt Romney

Republican presidential candidate, former Massachusetts Gov. Mitt Romney speaks during a campaign stop at the Music Man Square in Mason City, Iowa, Dec. 29, 2011.

Rick Santorum

Republican presidential candidate, former Pennsylvania Sen. Rick Santorum is surrounded by media after arriving at a campaign stop at Buffalo Wild Wings on Dec. 30, 2011 in Ames, Iowa. Republican presidential candidates are largely shifting from persuading voters to mobilizing them for Tuesday's caucuses.

Rick Perry

Republican presidential candidate, Texas Gov. Rick Perry, right, walks with former Marine officer Dan Moran during a campaign stop at Bayliss Park Hall, Dec. 14, 2011, in Council Bluffs, Iowa.

Michelle Bachmann

Republican Presidential candidate, Rep. Michele Bachmann, R-Minn. meets with patrons at the Nodaway Diner during a campaign stop, Dec. 28, 2011, in Greenfield, Iowa.

Newt and Callista Gingrich

Republican presidential candidate and former House Speaker Newt Gingrich speaks during the Iowa Veterans Presidential Candidate Forum as his wife Callista looks on, Dec. 10, 2011, in Des Moines, Iowa.

Rick Santorum

Rick Santorum, former senator from Pennsylvania and Republican presidential hopeful, walks from the corn during a campaign stop at the farm where the 1989 Movie 'Field of Dreams' was filmed on August 9, 2011, in Dyersville, Iowa.

Herman Cain

Republican presidential candidate Herman Cain, a businessman from Georgia, talks to voters following a stump speech at the Des Moines Register's Soapbox during the second day of the Iowa State Fair August 12, 2011 in Des Moines, Iowa.

Rick Perry

Rick Perry buys a vegetarian corn dog at the Iowa State Fair August 15, 2011 in Des Moines, Iowa.

Mitt Romney

Republican presidential candidate Mitt Romney and Sen. Chuck Grassley, R-Iowa, greet one another before heading to the Iowa Pork Producers Association pavilion to flip pork chops at the Iowa State Fair on August 11, 2011 in Des Moines, Iowa. Romney was at the fair to greet people and engage in traditional Iowa campaigning rituals.

Michele Bachmann

Republican presidential candidate, Rep. Michele Bachmann, speaks during a Faith and Family Council news conference on Oct. 4, 2011, in Des Moines, Iowa.

Newt Gingrich

Republican presidential candidate, former House Speaker Newt Gingrich speaks during a town hall meeting with employees at the Principal Financial Group on Sept. 29, 2011, in Des Moines, Iowa.

Rick Santorum

Rick Santorum, former senator from Pennsylvania and Republican presidential hopeful, gets a hug from Leslie Nussle and her daughter Sarah during a campaign stop at the Pizza Ranch on August 9, 2011, in Manchester, Iowa.

Ron Paul

Republican presidential candidate and Texas congressman Ron Paul speaks at the Iowa Straw Poll on August 13, 2011 in Ames, Iowa. Paul came in second right behind congresswoman Michele Bachmann.

Rick Perry

Republican presidential candidate Texas Governor Rick Perry visits with Erl Schmiesing of Waterloo, Iowa, during the Blackhawk County Republican annual Lincoln Day Dinner at the Electric Park Ballroom on August 14, 2011 in Waterloo, Iowa.

Mitt Romney

Former Massachusetts governor and Republican presidential hopeful Mitt Romney held a business roundtable to discuss the economy during a campaign stop at the Vermeer Corporation on August 10, 2011 in Pella, Iowa.

Ron Paul

Sen. Rand Paul, R-Ky., listens to his father Texas Congressman and Republican presidential hopeful Ron Paul in Cedar Rapids, Iowa on August 10, 2011.

Rick Perry

Republican presidential hopeful Texas Gov. Rick Perry speaks during the Johnson County GOP Fall BBQ at Clear Creek-Amana High School on Oct. 7, 2011, in Tiffin, Iowa.

Newt Gingrich

Former House Speaker and GOP presidential candidate Newt Gingrich speaks during an appearance at the Kiwanis Club luncheon at the Holiday Inn Five Flags on May 16, 2011 in Dubuque, Iowa.

Michele Bachmann

Republican presidential candidate Minnesota congresswoman Michele Bachmann greets guests at the Black Hawk County GOP Lincoln Day Dinner on August 14, 2011 in Waterloo, Iowa.

Rick Santorum

Rick Santorum and his wife Karen Santorum follow a bagpiper while greeting people outside the Hilton Coliseum.

Herman Cain

The campaign coach for Herman Cain arrives at the Stephens Auditorium at Iowa State University for the Republican party debate on August 11, 2011 in Ames, Iowa.

Jon Huntsman

Republican presidential candidate former Utah Gov. Jon Huntsman speaks during the Iowa GOP/Fox News Debate on August 11, 2011 at the CY Stephens Auditorium in Ames, Iowa.

Mitt Romney

Mitt Romney introduces himself to voters at the Iowa State Fair on August 11, 2011 in Des Moines, Iowa.

Michelle Bachmann

Michele Bachmann speaks at a Tea Party Express Rally at Waterworks Park on August 31, 2011 in Des Moines, Iowa.

Ron Paul

Republican presidential candidate Rep. Ron Paul greets visitors at the Iowa State Fair on August 12, 2011 in Des Moines, Iowa.