Cash is pouting into the Newt Gingrich campaign for the Republican presidential nomination after the stunning surge and upset victory over Mitt Romney.

Until this past weekend, Mitt Romney, the super-rich former governor of Massachusetts, had appeared to be cruising to the Republican presidential nomination, as lacklustre contestants scattered all around. Now he has a real opponent in the former Speaker of the House of Representatives, Newt Gingrich. The Republican primary season, which reaches its next stage in the ultra-swing state of Florida next week, now looks set to be longer, and more expensive, than Mr Romney or his supporters must have hoped. Not for the first time South Carolina has changed the dynamics of a US presidential race.

Newt Gingrich stormed to a shock victory over Mitt Romney in the South Carolina primary today, scrambling the race to choose a Republican challenger to President Barack Obama.

Romney flounders over tax as Gingrich piles on the pressure in South Carolina. By Rupert Cornwell

The race for the Republican presidential nomination took several twists and turns as Rick Perry dropped out, Newt Gingrich faced stunning allegations from his ex-wife and Mitt Romney struggled to maintain a shaky front-runner's standing.

Texas Governor Rick Perry abandoned his presidential bid and endorsed Newt Gingrich today, just two days before the pivotal South Carolina primary.

Republican front-runner under pressure to make public his returns ahead of South Carolina primary

Candidate's departure and support for moderate rival prompts calls among conservatives to unite

Jon Huntsman suspended his bid for the Republican presidential nomination today, calling on his party to end "an onslaught of negative and personal attacks" in the campaign and then endorsing rival Mitt Romney.

Mitt Romney, the front-runner in the race for the Republican US presidential nomination, handed over a fistful of cash to an unemployed supporter at one of his rallies on Saturday night, after she complained of being so hard-up that she could not afford her electricity bills.

Out of America: One of the oddest aspects of the Republican race is how little mention there is of the favourite's faith

The long journey to the White House seldom offers a chance to see a high-flying candidate speak candidly. By David Usborne

The long journey towards the White House seldom offers a chance to see a high-flying candidate speak candidly – with no script or stage management. But there is one place where guards are dropped... David Usborne climbs aboard

David Usborne joins bullish Republican frontrunner on journey to South Carolina