Correction:
His secretary, Rose Mary Woods, admitted to mistakenly making a single erasure of 4½ to 5 minutes on the tape while making a phone call but she strongly denied making the entire 18½ minute erasure. Later she conceded that she may have erased between 5½ and 6 minutes of the tape, but no more than that.
Nixon's critics allege that the erased portion contained incriminating evidence pertaining to the Watergate cover-up but of course they had no way of knowing what was really said on the erased portion of the tape.
No one outside of the Nixon inner circle could ever know what actually was on the missing 18½ minutes or exactly how and by whom the eull erasure occurred.
What high crime/misdemeanor did he commit?....Nobody has elucidated on that at all, yet.