He was cozy to varying degrees with all with all U.S. Presidents
(Truman called him a "counterfeit") but was especially chummy with the odious,amoral Nixon whom he carried water for on occasion and they bonded over their antisemitism as noted in that Americans United article above. He lied about his remarks when they were revealed in Haldeman's book and didn't "repent" until they were proven true with the release of the White House recording. Truman had him pegged.