Republican presidential candidates head to Iowa

Cedar Rapids, Iowa: Texas congressman and Republican nomination hopeful Ron Paul listens as he is introduced by his son Senator Rand Paul Photograph: Scott Olson/Getty Images

Clive, Iowa: Republican presidential hopeful Michele Bachmann pulls one of her campaign T-shirts off of a screen printing machine while visiting Competitive Edge, an advertising and promotion product manufacturer Photograph: Chip Somodevilla/Getty Images

Davenport, Iowa: Ron Paul speaks at a campaign rally Photograph: Brendan Hoffman/Corbis

Des Moines, Iowa: A supporter of Mitt Romney for the Republican nomination signs in guests at a table Photograph: Jim Young/Reuters

Humboldt, Iowa: Evan Smith of Sarasota, Florida, sells Michele Bachmann at a rally Photograph: Chip Somodevilla/Getty Images

Humboldt, Iowa: Michele Bachmann speaks to reporters on the campaign trail Photograph: Brendan Hoffman/Corbis

Humboldt, Iowa: Tim Pawlenty (centre) takes a tour of the Chantland-MHS manufacturing plant Photograph: Chip Somodevilla/Getty Images

Humboldt, Iowa: Michelle Bachmann speaks at a rally Photograph: Chip Somodevilla/Getty Images

Humboldt, Iowa: Republican presidential hopeful Tim Pawlenty (in white) makes the pledge of allegiance at the beginning of a campaign stop Photograph: Brendan Hoffman/ Brendan Hoffman/Corbis

Humboldt, Iowa: Tim Pawlenty speaks at a campaign rally Photograph: Brendan Hoffman/ Brendan Hoffman/Corbis

Manchester, Iowa: Rick Santorum, former US senator from Pennsylvania who is competing for the Republican nomination, shakes the hands of supporter during a campaign stop at the Pizza Ranch Photograph: Scott Olson/Getty Images

Pella, Iowa: Mitt Romney participates in a discussion about the economy with a group of business leaders at the Vermeer Corporation Photograph: Scott Olson/Getty Images

Pella, Iowa: Mitt Romney speaks to reporters Photograph: Jim Young/Reuters

Roland, Iowa: Rick Santorum leaves a campaign stop Photograph: Brendan Hoffman/ Brendan Hoffman/Corbis

Roland, Iowa: Supporters of Rick Santorum put up a sign at a farm where he held a campaign stop Photograph: Brendan Hoffman/ Brendan Hoffman/Corbis