Former Republican presidential contender Mike Huckabee, interrupted on Friday by a loud crash as he spoke to the National Rifle Association, joked that the noise was Democratic candidate Barack Obama falling off a chair as he dodged a gun aimed at him.
Huckabee later apologized for the remark.
"That was Barack Obama. He just tripped off a chair. He was getting ready to speak and somebody aimed a gun at him, and he dove for the floor," Huckabee told the NRA convention in Louisville, Kentucky, in comments that aired on CNN.
Democratic front-runner Obama, who if elected in November would be the first black U.S. president, was campaigning in South Dakota on Friday as he tried to wrap up the party's nomination.
The memory of the assassination of civil rights leader Martin Luther King 40 years ago, and the risks Obama could face in his run for the presidency, have been a concern of many voters during this presidential campaign.
At Obama's request the U.S. Secret Service began protecting him in May 2007, 18 months before the general election and the earliest a presidential candidate has received protection.
Huckabee later issued a statement saying he did not intend his "offhand remark" to offend or disparage the Illinois senator. "I apologize that my comments were offensive, that was never my intention," he said.
Republican presidential candidate John McCain also spoke to the influential gun-rights group on Friday as he sought to rally conservatives' support for his candidacy. The Arizona senator had warned that Obama and fellow Democratic candidate Hillary Clinton, a New York senator, would threaten gun-owners' right to bear arms if either was elected president.
McCain and Huckabee, a pastor and former Arkansas governor, have avoided answering questions about whether Huckabee could be McCain's vice presidential running mate.