Without a major earlier POD, whichever party wins the White House in 1980 is almost certainly headed for a massive victory in 1984 as the business cycle recovers. If Reagan loses in '80, it's tough to imagine him gearing up for a futile run in '84 against whomever the Democrats nominate.
The overwhelming favorite -- and the establishment candidate -- would obviously be the two-term incumbent, Vice President Walter Mondale (!), who's probably the face of the Democratic Party ITTL (!!). But, you know, overwhelming favorites sometimes come up a little short, like Hillary Clinton in 2008.
Gary Hart will probably still run as an outsider in '84, or he may sit out thinking that his best chance will be in '92 (when he'll be just 56 years old).
Dale Bumpers is probably the best Southern candidate in '84; Lloyd Bentsen was more of a political insider than a national campaigner, despite the gravitas he brought to the Dukakis ticket, and Al Gore is still in the House of Representatives in '84.
So long as you haven't butterflied away The Right Stuff, John Glenn probably still runs, and, like OTL, is quickly shown to be less than the sum of his parts on his resume. Ditto Fritz Hollings, who might not even run.
Then you have the folks who ran in '88 who would probably throw their hat in the ring in '84 ITTL: Dick Gephardt, Joe Biden, Bruce Babbitt, and Paul Simon. In a vacuum, Gephardt is arguably the strongest campaigner of that group, but his natural base of support (the midwest) is going to be fairly committed to Mondale. Similarly, Biden would have a potential opening as the "fresh young face," but most of that oxygen will be going to Hart. Babbitt and Simon aren't going to be a factor.
Finally, you've got Jesse Jackson, who, I imagine, will be Jesse Jackson.
Out of this group, I still think the smart money's on Mondale. Then the question becomes: without the need for a desperation gamble to try and make up a 20-point deficit in the polls, who does Mondale pick as his VP? Under the same traditional selection criteria that led to Mondale himself being Carter's VP, you'd probably be looking at a conservative southern governor to balance out a liberal midwesterner: that screams Reubin Askew. Hart and Bumpers are probably on the shortlist, and maybe even Biden.
These would be interesting times.