So how does he compare to other contenders by age? (Limiting it only to the two major parties. I know Thurmond lived to 100, but he was 3rd Party.)
Alf Landon also lived to 100. While not as long as Thurmond, he did love 50 years after he was first nominated. I can't think of anyone else who beat McGovern's 40 years alive from first being nominated. Carter narrow beats Hoover for 36 years at longest lived since first inaugurated.
What's amazing is that right before McGovern died, the Democratic Presidential nominees of all 11 Democratic conventions since the rules were changed to be more democratic (which McGovern was behind) were still alive. This is the first time a Democratic nominee for President chosen by a national primary system has died.
The reforms were really needed. If you look at the 1968 map here, most states didn't have a primary, and Humphrey didn't even run in the primaries. McCarthy got the most votes, and with RFK assassinated, had almost half of the votes for living candidates.
http://en.wikipedia.org/wiki/Democratic_Party_presidential_primaries,_1968