I can't say definitively whether the 1988 election could have "flipped" this way, but I can address it based on current law.
First of all, there are no federal restrictions on how electors vote, aside from the procedure specified in the 12th amendment ("cast a vote for President and a vote for VP, one of which has to be from a state that isn't yours"). Everything else boils down to "Follow your state laws."
As for the state laws, 24 of them place no restrictions on their electors, making it trivial for their party to tell them "Vote this other way".
For the remaining 26, it will vary from state to state. California, for instance, says:
The electors, when convened, if both candidates are alive,
shall vote by ballot for that person for President and that person
for Vice President of the United States, who are, respectively, the
candidates of the political party which they represent, one of whom,
at least, is not an inhabitant of this state. (§ 6906)
So in CA, if the party decided to flip, the electors would be compelled to go along with.
For another example, while North Carolina doesn't explicitly say that the elector has to vote for their party's candidate, it does provide for penalties if they don't:
Any presidential elector having previously signified his consent to serve as such, who fails to attend and vote for the candidate of the political party which nominated such elector, for President and Vice-President of the United States at the time and place directed in G.S. 163-210 (except in case of sickness or other unavoidable accident) shall forfeit and pay to the State five hundred dollars ($500.00), to be recovered by the Attorney General in the Superior Court of Wake County. In addition to such forfeiture, refusal or failure to vote for the candidates of the political party which nominated such elector shall constitute a resignation from the office of elector, his vote shall not be recorded, and the remaining electors shall forthwith fill such vacancy as hereinbefore provided. (§ 163-212)
I haven't looked at the other 24 state's laws (I just picked those two at random), but the odds are good that the rest have similar language. The real question is whether it's possible for a party to change its candidate mid-cycle. That's even harder to track down, since states may not even have that codified into law. California, for example, simply directs the state's Secretary of State to handle it.
I suspect that this is only something a party would do in the most desperate straits. The possibility of lawsuits and other challenges that could distract from the election, even if it turns out to be perfectly legal, on top of the the appearance of uncertainty it conveys to the electorate as a whole, means it's most likely better to lose the election than to damage your party's image across all branches of government.
A better alternative might be to have the presidential candidate withdraw himself entirely, bump the VP candidate, and have them choose a new VP. You'd have to have a pretty carefully managed crisis to pull it off, though. Something like a major car accident, a death in the family which causes a withdrawal from politics, etc.
If the presidential candidate ever happens to die during primary season, we'll likely find out the actual answer to this.