That grace in this country started dying in the 20th Century and died with FDR. That's why the 22nd Amendment had to be adopted. In Russia, there never was such grace. Tsar Vladimir will rule the New Russian Empire until he is overthrown or dies.
Richard Nixon had the good grace not to contest the close election of JFK. Now that we know what we know about the Democrat Party, maybe he should have. Not that it would have changed their behavior towards him. I think history will be kinder to him that even the GOP and conservatives have been.