"He knows that young men and women in uniform are not reliable votes for him," he said.
Coffman released a written apology saying he "misspoke" on Wednesday night, according to multiple reports.
"I have confidence in President Obama’s citizenship and legitimacy as president of the United States," he said in the statement, disassociating himself from the so-called "birther" conspiracy theory that claims Obama was not born in the United States, or that his parents were not naturalized citizens at the time of his birth, thus making his presidency illegitimate.
"However, I don't believe the president shares my belief in American exceptionalism," Coffman continued. "His policies reflect a philosophy that America is but one nation among many equals. As a Marine, I believe America is unique and based on a core set of principles that make it superior to other nations."
The GOP presidential candidates have often attacked Obama on the issue of exceptionalism as well. Obama in April defended his record on the subject, saying his entire career is "a testimony to American exceptionalism."