...Mondale won the primaries. The contenders were Mondale, Gary Hart and Jesse Jackson. Generally, Hart was favored in the west, while Mondale was favored in the east. The total popular vote in the primaries was pretty even between Mondale and Hart. I think Jackson won only 2 primaries, Louisiana and South Carolina. In the June "Super Tuesday" primary, Mondale reached the number of delegates to get the nomination. The nomination was historic, since (the late) Geraldine Ferraro was the first woman to be nominated on a major-party ticket. This is just a bare-bones summary and there's a lot more to it, so if you want to read about that campaign in depth I'm sure there are plenty of sources. I can't come up with a more in-depth answer as to why Democrats favored Mondale. I guess part of it was that his name was far more known than Hart's at that time.

The sweet young thing was Donna Rice, but that scandal didn't happen until 1988. Hart was clean as a whistle in 1984.

Mondale would have the inside track for running. Some politicians would not run against him recognizing it was 'His turn." That is an element of politics that is not discussed but is a factor.

In the 1980 primaries Ted Kennedy ran against Carter, but ultimately lost the nomination in the primaries. I remember Kennedy's speech at the 1980 convention as one of the great convention speeches. I am pretty sure that after that Kennedy decided not to run for President any more. I'd have to look that up, but that is my memory. If Kennedy had not decided that, he could have been one of the contenders in 1984. However, Reagan was still wildly popular in 1984; things didn't start falling apart for him until his second term. So frankly I think whoever the Democratic nominee could have been in 1984, they probably would have been a "sacrificial lamb" because Reagan was just too popular at that time.

I wonder why Kennedy didn't run?

I get that Mondale was a senior statesman in the party, but Kennedy was too. And nominated Carter's VP to run against Reagan would be like the GOP nominating Cheney to run against Obama in 2012.

I'd have to sit down and read a biography of him, but I'm guessing that he felt he could have a longer and more productive career as a Senator - and he was for almost 47 years. So I assume that was the main reason.

I guess some felt they "owed it to him" in a way. I remember Mondale being a pretty good candidate, except that he experimented with telling the truth about raising taxes - that didn't go over too well. Reagan was denying it as I remember, but then did it anyway.