The Sanders campaign wasted no time to return fire against David Brock, the head of the pro-Hillary Clinton super PAC Correct the Record. Brock attacked the Vermont senator over a Sanders campaign ad that Brock claimed was a “significant slight to the Democratic base.”

“From this ad it seems black lives don’t matter much to Bernie Sanders,” Brock told the Associated Press.

Brock previously attacked Sanders over the Vermont senator’s socialist background and demanded Sanders release his medical records.

The Media Matters chief said on Bloomberg TV’s “With all Due Respect,” that Sanders has “got a 30 year history of affiliation with a lot of whack-doodle ideas and parties. Think about what the Republicans will do with the fact that he’s a socialist in the fall.”

Sanders’ spokesman Michael Briggs released statement on Thursday about “Hillary Clinton mudslinger David Brock.”

“Bernie Sanders, as everyone knows, has one of the strongest civil rights records in Congress. He doesn’t need lectures on civil rights and racial issues from David Brock, the head of a Hillary Clinton super PAC. Twenty-five years ago it was Brock – a mud-slinging, right-wing extremist – who tried to destroy Anita Hill, a distinguished African-American law professor. He later was forced to apologize for his lies about her. Today, he is lying about Sen. Sanders. It’s bad enough that Hillary Clinton is raising millions in special-interest money in her super PACS. It is worse that she would hire a mudslinger like David Brock. She should be ashamed of her association with Brock.”

Recent polls are showing Sanders ahead of Clinton in New Hampshire and Iowa.

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