Ben Carson said in an interview published Tuesday that President Obama was “raised white” and can’t understand the African-American experience the way he can.

“He’s an ‘African’ American. He was, you know, raised white,” he told a Politico podcast. “I mean, like most Americans, I was proud that we broke the color barrier when he was elected, but … he didn’t grow up like I grew up … Many of his formative years were spent in Indonesia. So, for him to, you know, claim that, you know, he identifies with the experience of black Americans, I think, is a bit of a stretch.”

Ben Carson speaks during a town hall event on Feb. 21 in Reno, Nevada. Marcio Jose Sanchez / AP

The Republican presidential candidate finished sixth out of six in South Carolina; after peaking in November, he’s been polling at the bottom of the pack and struggling to turn supporters into voters. Carson’s rags-to-riches journey from impoverished the inner city of Detroit to an internationally renowned career as a pediatric neurosurgeon first got him on the national stage, but it’s this kind of inflammatory criticism of the president that got him on the radar of conservatives nationally and drafted him to run for president.

Carson long dismissed questions about race as divisive and downplayed his own race, but in these final days he’s dug into race as a campaign issue, running ads against affirmative action in South Carolina and condemning black crime as “a crisis” that only he knows how to overcome.

These attacks are nothing new: critics have been arguing that the president is too black – or not black enough – since he appeared on the political stage. Rupert Murdoch came under fire earlier last year for suggesting that Carson could be the “real black President who can properly address the racial divide,” while Rush Limbaugh has argued that Obama “disowned” his white side.

The president himself has addressed the issue at length.

“Sometimes African Americans, in communities where I’ve worked, there’s been the notion of “acting white”—which sometimes is overstated, but there’s an element of truth to it, where, okay, if boys are reading too much, then, well, why are you doing that? Or why are you speaking so properly?” he said in the summer of 2014. “And the notion that there’s some authentic way of being black, that if you’re going to be black you have to act a certain way and wear a certain kind of clothes, that has to go.”