Has either political party ever sent the same nominee into the general election twice
The Democrats did it numerous times. And lost every time they tried it.
1896 William Jennings Bryan
1900 William Jennings Bryan
1908 William Jennings Bryan
1952 Adlai E. Stevenson II
1956 Adlai E. Stevenson II
Reagan almost took the nomination from Ford and then the next time around won the nomination.