No. 1984 wasn't winnable for any Dem under any circumstances. If one purely went of the economic growth numbers of the first quarter of 1984....you'd know any Dem was doomed regardless of whether or not even Jesus Christ himself was given the VP slot:
Prof. Edward R. Tufte of Yale University, a political scientist who specializes in the relation between the business cycle and the electoral cycle, estimates that real disposable income will rise by 4.4 percent this year. That promises to be the second-strongest economic advance in personal income since World War II in any election year in which the incumbent President was seeking a second term.
The only President to face an election with stronger income growth going for him was Lyndon B. Johnson.
https://www.nytimes.com/1984/04/11/business/economic-scene-real-income-and-elections.html
