Newt Gingrich joins the presidential Republican candidates – in pictures

Newt Gingrich: A Republican heavyweight, but he may be a decade too late. In 1994, he helped the Republicans take Congress for the first time in 40 years. He is regarded by Republicans as a noisy source of innovative ideas. But, at 67, the former House Speaker may be seen by voters as too old. His turbulent private life could also be a problem. Only an outside chance. Photograph: Alex Brandon/AP

Herman Cain: The only African-American candidate in a party still overwhelmingly white. The former chief executive of Godfather’s Pizza was little known outside Georgia until he entered this race. Made an impression in the first party debate by being outspoken, but has never held elected office and is short on policy, repeating often that he will choose experts then listen carefully to their advice. No hoper. Photograph: Mark Hirsch/Zuma Press

Mitt Romney: He ran John McCain hard for the Republican nomination in 2008 and has millions of his own money to squander. But he is poor speaker, lacks charisma, and conservative Republicans are suspicious of his record as governor of Massachusetts, where he introduced a health care programme similar to Obama’s. His Mormonism is also viewed with suspicion by Christian evangelicals. In spite of this, he will almost certainly be one of the front-runners. Photograph: Julie Jacobson/AP

Jon Huntsman: The major drawback, for Republicans, is that this former governor of Utah served in the Obama administration as US ambassador to China until this year. A former keyboard player in a rock band and son of a multi-millionaire, he is setting up a political action committee, the first step in seeking the Republican nomination. Like Romney, his Mormonism may be a problem. An outsider. Photograph: Philippe Lopez/AFP

Tim Pawlenty: The former governor of Minnesota was the first serious candidate to announce. His main selling point is his success in winning the governor’s race in a Democrat-leaning state and, in office, erasing Minnesota’s $4.8bn deficit. More than a bit on the boring side, with his recent book, Courage to Stand, said to be one of the most tedious political biographies of all time. An outsider. Photograph: Mark Hirsch/Zuma Press

Donald Trump: The wildest of wild cards. The mega-rich businessman has not formally committed to standing and may be just enjoying the publicity. Took a hammering two weeks ago when his championing of the Birther issue left him looking foolish after Obama released his long-form birth certificate, demolished Trump with jokes at a dinner and then Bin Laden was killed. But he is still pulling in the crowds. Photograph: Steve Marcus/Reuters