Newt Gingrich has confirmed that he is ending his campaign to win the Republican nomination to challenge Barack Obama for the US Presidency.
Mr Gingrich ended his run after dazzling in televised debates but slumping to defeat in Republican primaries under a barrage of attack ads portraying him as a Washington insider.
The former US House of Representatives speaker was badly trailing front-runner Mitt Romney in polls and his campaign piled up a debt of $4.3m.
Mr Gingrich stopped short of endorsing Mr Romney but said voters had a clear choice in November's general election between President Obama and the former Massachusetts governor.
"I am asked sometimes - is Mitt Romney conservative enough? And my answer is simple: compared to Barack Obama?" Mr Gingrich said.
"This is not a choice between Mitt Romney and Ronald Reagan. This is a choice between Mitt Romney and the most radical, leftist president in American history."
Mr Gingrich, who announced his departure from the White House race in a long statement in Arlington, had scaled back his campaigning for weeks after cutting staff.
With wife Callista by his side, Mr Gingrich described his year-long presidential campaign as "truly a wild ride".
"I could never have predicted either the low points or the high points. It was all sort of amazing and astonishing," he said.
