Independent Vermont Senator and Democratic presidential candidate Bernie Sanders saw his support among black voters crater by more than half in a national poll amid a roiling controversy over his decision to brag about an endorsement by comic Joe Rogan, and stand by it after the comic’s history of bigoted remarks emerged.

Sanders was enjoying a bit of a surge with black voters in the weekly Economist/YouGov poll, going from 12 percent three weeks ago to 17 percent the following week in a poll that was taken two days after Sanders tweeted a video of Rogan praising the candidate’s consistency and saying he would “probably” vote for Sanders.

But in the most recent poll, taken Sunday through Tuesday of this week, Sanders’ support among black voters has plunged to eight percent.

There’s no way of telling exactly what caused the swing, but the Rogan controversy began to erupt just before last week’s poll was taken, as past comments by Rogan — including a clip in which he compared a black neighborhood to the fictional Planet of the Apes — began circulating, and the Sanders campaign responded by standing by their embrace of the endorsement in spite of those comments.

Since then, Rogan has clarified his statements about Sanders, distancing himself from the notion that he was endorsing Sanders. On his podcast, Rogan said “All I said is I’m probably gonna vote for him,” but added “I like Tulsi Gabbard…I love her, I love him, I love Andrew Yang.”

“Here’s the really important point: I’m a fucking moron,” Rogan added, and went on to say “I don’t know what’s required to be President, and that :maybe we’re better off with Trump. Maybe we’re better off with someone else. I don’t know.”

There were other controversies this week, including the booing of former Secretary of State Hillary Clinton at a Sanders rally and a less-reported reemergence of comments Sanders made in the 1970s mixing praise with condemnation of racist then-Alabama Governor George Wallace.

The poll was also taken while the Iowa caucuses — a contest which Sanders was favored to win — were devolving into chaos. Sanders heads into New Hampshire with a big polling lead, after which he and former South Bend Mayor Pete Buttigieg will have a chance to test the trope that early state wins can translate into gains with black voters.

Elsewhere in the same poll, former Vice President Joe Biden maintained a massive lead among black voters, but his support did slip slightly, from 46 to 43 percent, while former New York City Mayor Mike Bloomberg — who has spent over a quarter of a billion dollars on ads so far — surged from three to 11 percent, and Mayor Pete ticked up three points with black voters — from one percent to four. Massachusetts Senator Elizabeth Warren was the only other candidate in double digits with black voters, maintaining 14 percent in both polls.

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