The DNC changed their rules to make it harder to get on the primary if they didn't like you. It's difficult finding the timeline of DNC rules, so take that with a grain of salt.
With the premise thqt being a good president =/= being a good person:
Washington
Adams
Jefferson
Lincoln
FDR
Wilson
Carter
Sorta LBJ as long as you don't think he was involved in JFK death
And phucket Obom'ner, you have to admit he was nationally gridlocked but it was a much better time for America plus Obamacare saved and improved lives