What's the most an incumbent governor has ever lost by?
Lief, his loss would be historic!!! No PA governor has ever been defeated.
Actually, no. While it has not happened in modern times, incumbent governors of PA have been defeated before.
1820: Incumbent William Findlay was defeated by Joseph Hiester.
1835: Incumbent George Wolf was defeated by Joseph Ritner.
1838: Incumbent Joseph Ritner was defeated by David Porter.
1851: Incumbent William F. Johnston was defeated by William Bigler.
1854: Incumbent William Bigler was defeated by James Pollock.
It is also worth noting that from 1874-1968, PA governors were not allowed to serve consecutive terms, so while part of the reason we haven't seen an incumbent defeated since 1854 is because PA has had governors who were seen as good by the people of PA, the other part of the reason that the last time an incumbent was defeated was back in 1854 was indeed because of the fact that defeating an incumbent was impossible for nearly a century in PA because incumbents could not legally run for consecutive terms.
So, in short, Corbett's loss wouldn't be historic. It would be historic if we only look back 159 years, but if we look back further, we can find a total of 5 instances where incumbent governors of PA were defeated when they attempted to run for re-election.