Well certainly , he could have done better then he did(I mean he only barely won one state, and electorally did worse then McGovern). The best he can do in my opinion though is this:
This actually looks like a fairly realistic "best case" scenario for Mondale, maybe throw in a few random states like New York, West Virginia, Washington, Hawaii into the mix....
The problem with Mondale was that only did he somehow seem to appear to be older than Reagan in terms of optics, but additionally he was widely seen as an establishment Democratic candidate, as the former Veep of unpopular President Jimmy Carter (Who only won six states in 1980) running against an extremely charismatic and personally popular Ronald Reagan.
Although Reagan's personal favs were high in '84, many of his economic and foreign policy platforms were not....
Certainly we would not expect Mondale to perform well in the "Deep South", compared to Carter in '80, however it appears that in '84 Reagan was able to bag a huge chunk of John Anderson '80s voters, which sealed his fate in the Suburbs of Northern States.
Now, back in the days when TV campaign commercials were much more influential than today, this classic Reagan '84 ad does a compare & contrasts, but with an upbeat and optimistic theme...
https://www.youtube.com/watch?v=EU-IBF8nwSYThe Democratic establishment selection of Mondale as their candidate in '84 was an awful choice that reminded voters of the economic pains of the late '70s ("Stagflation") rather than hitting Reagan on the economic austerity regime that caused widespread recession and poverty throughout our great country.