Incumbency is an advantage unless (1900 on, implying also chances of an incumbent running for a third term for which he is Constitutionally eligible )
1. one's party splinters (1912)
2. one's grand dream of foreign policy implodes (1920)
3. the economy collapses (1932)
4. a war goes badly (1952, 1968)
5. one is an incompetent campaigner for President (1976)
6. a gross embarrassment happens in foreign policy (1980)
7. one has no idea of what to do in a Second Term (1992)
I see multiple reasons for Donald Trump to lose a re-election bid: extremism, corruption, abuse of power, and perhaps a trade war that goes badly.
Ford ran probably the best losing campaign by any candidate since maybe Hughes in 1916.
He really didn't. Between "drop dead NY", no Soviet Domination, and his failure to explain what made Nixon more special than draft dodgers, I'd argue he did worse than Gore or Hillary.
No, Carter simply ran the worst winning campaign.
