Mondale was able to sell two things, both entirely true:
1) That the U.S. military build-up had actually begun during Carter's last year, and
2) He would tact back to the middle from Reagan's excesses.
=========
And Mondale didn't go hog wild seeking endorsements during the Democratic primary. Basically after receiving the AFL-CIO's endorsement and a few other tradition labor unions, he decided he had enough. Even being interviewed on one network President Mondale said, I mean at that time Vice-President Mondale said, I have enough endorsements, It's time for the people to decide. And he went on to good-naturedly banter with the anchor, Believe it or not in this business of politics, you can have too many endorsements.
I've seen one kind of way-out ATL in which Mondale receives the endorsement of the American Federation of Teachers endorsement, which following less than a year after Reagan's commission on education and national report card, proved a very mixed bag and actually somewhat unpopular. And he follows this up by seeking and receiving a whole packel of endorsements from all sorts of groups, and the feeling among voters of course is that he's promised everything to everyone. Don't think a seasoned political pro would make this mistake.