Sen. Bernie Sanders (I., Vt.) said Wednesday that he did not know at the time that Russian trolls promoted his 2016 presidential campaign and wondered why Hillary Clinton’s team did not do more to tell voters about the extent of Russia’s election interference.

In addition to their well-known efforts to boost Donald Trump, Russian trolls supported Sanders’ presidential primary campaign, when he mounted a surprisingly strong but ultimately unsuccessful challenge to Clinton, according to special counsel Robert Mueller’s indictment from last week.

Mueller’s team indicted 13 Russian nationals and three companies for interfering in U.S. elections from 2014 to 2016.

In an interview on Vermont Public Radio, Sanders took issue with a listener’s question that made it seem as if he knew about Russian bots promoting his candidacy at the time he was running.

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