Washington - Newt Gingrich is quitting the US Republican presidential contest after a tumultuous campaign that saw him go from longshot to front-runner and back again.
The final blow for the former House of Representatives speaker came on Tuesday night, when rival Mitt Romney easily won primary victories in five northeastern states that crowned him as the presumptive Republican nominee.
Gingrich had campaigned heavily in Delaware as the conservative alternative to Romney but he lost by nearly 30 percentage points there.
Clobbered by negative ads paid for by allies of Romney, Gingrich's campaign went downhill almost immediately after he won the South Carolina primary on January 21.
He will formally pull out next week, a Gingrich campaign official said on Wednesday.
Gingrich's idiosyncratic run turned grandiose ideas like establishing a moon colony into front-page fodder and descended into near farce last week when he was bitten in the hand by a penguin during a visit to a zoo in St Louis.
A bombastic campaigner who shed tears talking about his mother in Iowa, Gingrich enjoyed playing against type on the campaign.
He was strongest in televised presidential debates where he unleashed slashing attacks on Republican rivals, Democratic President Barack Obama and even debate moderators whom he suspected of liberal media bias.
But he won only two states in the primary season and made the decision to quit after receiving an early morning phone call on Wednesday from Romney, said Gingrich spokesperson R.C. Hammond.
Gingrich agreed to endorse the former Massachusetts governor next week although he has no aspirations to serve in a future Romney administration, Hammond said.
“Newt's next role in life is as a citizen,” Hammond said.
The 68-year-old seemed to enjoy himself to the end, when he scaled back on campaign rallies in recent weeks and visited zoos and museums while on the road.
“I never got the sense that he was quote-unquote down,” said adviser Charlie Gerow. “I got the sense on a couple of occasions that he was tired. Really tired.”
Gingrich's withdrawal further clears the way for Romney, who has now claimed the unofficial mantle of the Republican nominee in November's election against Obama.
The only Republican left in the race is libertarian Ron Paul who is miles behind Romney in polls and has not won a single nominating contest.
Gingrich provided a lesson in the power of the biggest force in this year's contest: the newly arrived independent “Super PACs,” political action committees that have no limits on how much money they can raise or spend in support of candidates.
Throughout the primary season, Gingrich depended on the largesse of a Super PAC called Winning Our Future, which received at least $21.5-million in donations from billionaire casino mogul Sheldon Adelson and his family.
At the same time, a pro-Romney PAC, Restore Our Future, spent $19-million on ads attacking Gingrich.
The Romney camp attacked him as a Washington insider, accusing Gingrich, who rose to be the most powerful Republican in the United States during his leadership of the House in the 1990s, as tainted by the ways of the nation's capital.
In part, Gingrich said, his campaign faltered because the country was not prepared for his big ideas.
“I haven't done a very good job as a candidate because it's so difficult to communicate big solutions in this country when the entire structure of the system is so hostile to it,” Gingrich told students at Georgetown University last month.
His candidacy never lacked drama. Days before Gingrich's victory in South Carolina, his second wife appeared in a television interview to accuse Gingrich of asking her for an open marriage while he was having an affair with his current and third wife Callista.
Gingrich vociferously denied the charge at a debate, the forum that helped give lift to his campaign.
Last summer, he suffered a staff exodus as advisers criticised his decision to take a Greek cruise with Callista, losing time that could be spent raising money and meeting voters.
Callista's smiling, often silent presence at campaign events offered a constant reminder of Gingrich's complicated private life, which turned some evangelical voters away from him. - Reuters