Former Texas governor Rick Perry has dropped out of the US presidential race, becoming the first casualty in a crowded battle for the Republican Party nomination in 2016.
"Today I am suspending my campaign for the presidency of the United States," Perry told a forum in St Louis, Missouri on Friday night (local time).
"I step aside knowing our party is in good hands, as long as we listen to the grassroots, listen to that call of conservatism."
Perry's campaign had been running on fumes for more than a month, reportedly suffering funding problems so severe that he could not pay many of his staffers.
It is the second time Perry, the longest-serving governor in Texas history, has folded up his presidential campaign tent.
The 65-year-old ran for the Republican presidential nomination in 2012. He finished fifth in the Iowa caucuses, the first voting contest in the race to determine the parties' nominees, and dropped out weeks later.
But this year's field was more crowded and competitive, and having never gained serious traction in the polls, he quit some five months before the first primary votes are cast.
Of the 17 major Republican candidates, Perry was polling at 13th, with less than one percent support, according to a RealClearPolitics poll average on Friday.
Tributes quickly poured in. "God bless Rick Perry for his continuing commitment to that cause" of conservatism, former Florida governor Jeb Bush, an early frontrunner in the race but now trailing billionaire Donald Trump, wrote on Twitter.
"He served in the United States Air Force and as governor of Texas with distinction, and I have no doubt that his service to our nation is not over," added fellow candidate Senator Marco Rubio in a statement.
"I commend him for running an honourable, positive campaign."
Perry was one of the candidates who clashed most openly with Trump, whose bombast and propensity to insult and mock his rivals has become a dominant character of the race.
In July, Perry blasted Trump as a "cancer on conservatism [that] threatens to metastasise into a movement of mean-spirited politics."
On Friday, he offered another, more veiled, jab at the real estate mogul and star of wildly popular television show The Apprentice.
"The conservative movement has always been about principles, not about personalities," Perry told the Missouri crowd.
"Our nominee should embody those principles. He or she must make the case for the cause of conservatism more than the cause of their own celebrity."
Trump had consistently trashed Perry on the campaign trail. But on Friday he tweeted that Perry "is a terrific guy and I wish him well - I know he will have a great future!"
Perry failed to make the top-10 cut in the first Republican debate, on August 6, instead joining the other low-polling candidates for an undercard event before the prime-time debate.
He had been set to join the low-pollers in the second debate, which is scheduled for September 16.