He puts together a winning progressive team, including union activists, economists, and just plain regular citizens. He addresses the main primary issue of loss of good-paying industrial jobs with not enough taking their place. That is, the decline of the American middle class. And people are convinced that Jackson and his team have some solid steps to try in the short- and medium-term.
Ronald Reagan runs a solid campaign, and even makes the same great joke about his age during the second debate, to which Jackson responds graciously. But Jackson's insurgent campaign beats the Gipper, and somewhat comfortably at that at 51-49%.
Bonus Points: Jackson makes the same tactical and moral error of calling New York City "HymieTown," but he does a much more heartfelt, better, and skilled job of recovering.