Can the Clintons sue the United States Government when Trump floats accusations of murder?

It seems there is so much that Trump can get away with saying without repercussions, but it got me wondering if the US government is free of slander laws every time Trump slanders a citizen without proof of a crime, since Trump is a government official. He retweeted a conspiracy theory that the Clintons had Epstein knocked off. If a regular public servant did that they would be fired and the city or state or federal government could be sued. So can the sue the US Government since there appears no way to stop the lies and accusations that the president spreads like butter.