I had a class with someone who has spent his entire career studying presidential elections and has written a few books on them. He said that before the modern convention process was established, there was actually an entire committee charged with finding the nominees for President and Vice President and informing them about their selection. In many cases even those actively campaigning for the nomination didn't attend the convention.
I think in many countries with 'strong' party systems, the party bosses essentially pick the candidates. For example, even in the UK to this day, if you live in a certain district can you run as the Conservative, Labour, or Lib Dem MP candidate for that district? ? ? I don't know. In 1991, one of my professors said no. If you're a newbie, some kind of committee assigns you a district, almost always a losing district. But if you do better than expected, they then assign you a little bit better district. And then maybe in three or four times, you get a district you can actually win. Now, that was almost twenty-five years ago and just according to one professor.
And maybe in earlier times, the U.S. had this 'strong' party system.
I do think that 1976 is a potential POD. Wanting to avoid how McGovern made such a mess of it in '72, and please remember, Carter was also an outsider much like McGovern, Carter announces his decision several weeks early. And he does so matter-of-factly in an effort to avoid embarrassing McGovern too much. In fact, I'd like to look up when the decision of Mondale was publicly announced.
On the Republican side, Ford has said that asking Rockefeller to bow out was one of the things he regretted. Reagan, in a somewhat desperate attempt, had the strategy of announcing three weeks before the convention that pro-union Pennsylvania Senator Richard Schweiker would be his running mate. On C-SPAN's Book TV, Craig Shirley author of
Reagan's Revolution said that this was a good gamble which changed a close but losing position into having at least some chance. And if Ford had picked a liberal choice, the convention may have revolted. But maybe not if he had done this three weeks early and people had plenty of time to make some calculations. I mean afterall, would you rather have President Ford or Governor Carter? So, I think there's some potential PODs on the Republican side, too.
Reagan announced his Schweiker selection on July 26, 1976.
http://www.bloombergview.com/articles/2012-08-26/the-last-up-in-the-air-convention
The Republican Convention opened on August 16, 1976.
http://www.presidency.ucsb.edu/data/convention_bounces.php