"Donald Trump doesn't mean anything to me," Rush told CNN. "He is not a president. He is the worst thing that has ever happened to the American presidency. He is the worst president, including ... Andrew Johnson."
Johnson became the first president to be impeached by the House of Representatives in 1868 and avoided being removed from office by a single Senate vote. He also vetoed early civil rights legislation and urged Southern states not to ratify the 14th Amendment.
Rush's comments were the latest criticism of President Trump's performance amid mass protests and following the death of George Floyd in Minneapolis police custody last month.
On Thursday, Trump held a round table in Dallas and promised to take steps to increase economic opportunities in minority communities, address the healthcare disparities faced by the black community, lobby Congress to enact school choice, and sign an executive order calling on police departments to adhere to the “most current standards on use of force.”
Sen. Tim Scott, R-S.C., the lone black Republican in the Senate, has been a prominent defender of the president's track record on African-American issues.
"The fact that we have secured permanent funding for HBCUs [historically black colleges and universities] under President Trump is something that was surprising, I think frankly, to the HBCUs [and] the United Negro College Fund," Scott told Fox News host Neil Cavuto on June 2.
"The president said clearly that the level of funding the last year was the highest ever. Think about the jobs created. Under this administration, we created over seven million jobs, two-thirds of those jobs went to minorities and to women. We had an increase the labor force participation rate among African-Americans," Scott added.
"Home ownership, I believe, was up by two points under this administration. Access to a quality education improved, help for sickle cell anemia secured under this president, so when you look at the actual accomplishments -- put aside all of the vitriol, all of the rhetoric, all of the things that some may find distasteful -- the actual policy positions have been incredibly concrete."
Fox News' Andrew O'Reilly contributed to this report.