5. Then the three I don't know as much about: Askew and Hollings could've made things interesting in the general, but good luck winning the primary. As for Cranston, idk.
Askew has a reputation as one of the greatest state governors of all time, and he is the one (amongst those who actually ran in the primaries) who might have made 1984 more interesting as far as I can tell.
Askew was conservative on certain social issues, for instance abortion and homosexual rights — in a sense he was something of a New Dealer. However, he was liberal enough on racial issues to appeal to most of the core Democratic non-white constituencies, and he would likely have been more appealing to the suburban Middle America than any Democratic nominee since Kennedy and Johnson.
Hollings might have been able to compete with Reagan as Carter did in the core of the South, but he would have lacked the appeal elsewhere much more than Askew. Cranston, who had the handicap of age — he was ten years older than Jimmy Carter and eight years older than George McGovern —
might have been able to attract more liberals to the polls as he had strong support among grassroots nuclear activists, but it is doubtful whether he could have avoided the problems McGovern ran into twelve years before.
Bruce Babbitt, who ran in 1988, and
Lloyd Bentsen, who of course was Dukakis’ running mate, were considered potential candidates though they did not run in the primaries (did Babbitt regret not running in 1984??), might have been better than most of those you list.