Alabama Republican Senate candidate Roy Moore said last year that he doesn't believe former President Barack Obama is a natural-born citizen.

"My personal belief is that he wasn't, but that's probably over and done in a few days, unless we get something else to come along," Moore said after being asked if Obama was a natural-born citizen last December, according to a video unearthed by CNN's KFile.

Moore is a longtime skeptic of Obama's citizenship and was a leading voice of the "birther" movement. The former judge has been calling into question the former president's citizenship as far back as 2008.

"I don't see any reason a candidate who has such a serious question would not come forward with the truth about where he was born," Moore said in 2008 during Obama's candidacy in an interview with Worldnetdaily.

The GOP Senate candidate was unclear in the video about how he defines a "natural-born citizen."

"My opinion is, there is a big question about that," Moore said after being asked his definition.

Moore finished ahead of incumbent Sen. Luther Strange in last week's Republican primary. The run-off election is set for Sept. 26.