Who was the last U.S. president to be faithful to their spouse?

Lets go back 50 years and go forward from there
LBJ ..absolutely faithful ..he was so ugly who else would want him?
Nixon..his own Watergate situation dominated his administrations so having something on side was never a priority
Ford…Absolutely faithful
Jimmy Carter..Absolutely faithful but he did Lust after the Statue of Liberty?
Reagan..cheated on his first wife..but with Nancy he was absolutely faithful
George HW Bush..Absolutely faithful
Clinton..never faithful..Flowers / Lewinsky..his list of women he boinked is long and distinguished
George W Bush…never cheated on Laura
Obama…Absolutely faithful
Trump…well…what exactly is Unfaithful
Biden…wanted to be unfaithful but apparently never went into the bedroom