Texas Governor Rick Perry has abandoned his presidential bid and endorsed Newt Gingrich, just two days before the pivotal South Carolina primary.
"I know when it's time to make a strategic retreat," Mr Perry told a news conference. He called Mr Gingrich "a conservative visionary who can transform our country" and added, "Newt is not perfect, but who among us is?"
Mr Perry had faced calls to drop out of the race to compel conservative voters, whose support has been divided among several conservative candidates, to rally behind Mr Gingrich in hopes of stopping Mitt Romney. Recent polls show Mr Gingrich gaining steam heading into Saturday's contest, but he still trails Mr Romney by about 10 percentage points.
Mr Romney has benefited so far from having several challengers who are considered more conservative than him competing for the same segment of voters.
Mr Perry's decision to endorse Mr Gingrich does not necessarily mean conservatives will rally behind him. Former Pennsylvania senator Rick Santorum, a champion of the anti-abortion issue, is still in the race and over the weekend was endorsed by a group of evangelical leaders.
Mr Perry entered the race last August to great fanfare and high poll numbers. But his standing quickly fell after a series of mistakes called into question whether the Texas politician, who had never lost a race during his three-decade career in elected office, was ready for the national stage.
His biggest error came in a nationally televised debate in early November, when he could not remember the name of the third Cabinet department he pledged to eliminate. "Oops," he said. Making fun of himself afterwards, he told reporters: "I stepped in it."
The showing gave the impression that Mr Perry could not articulate his own policies.
Mr Perry's speech to a New Hampshire audience in October led to a damaging video, during which he appeared unusually animated - "loopy" to some observers - a stark contrast to the image of the serious, starchy governor he had projected.
He also urged college students in New Hampshire to support his candidacy, "those of you that will be 21" on election day, though the voting age is 18.