Buyer's Remorse

Wikipedia says "Buyer's remorse" is an emotional condition whereby a person feels "remorse" or regret after a purchase.

I have heard it said that what might happen in today's primaries is a symptom of "buyer's remorse."

I assume this is metaphorical, but what does it mean?
Hopefully, nothing is literally purchased, but votes are cast.
What about the remorse?
Apparently, it's remorse for something that happened in a previous primary, in another state.

So, the voters in one state regret what other voters did in another state?
So, you can regret another person's actions?
I might resent or disapprove of another's acts, or wish they hadn't done them, but I don't regret other people's actions.

Or maybe the entire voting population in the United States of America is thought to be one agent. It votes one way in one set of primaries, and then if the poles in the states of subsequent primaries reflect a different trend, it must be regretting it's previous votes.

Neither of these interpretations make much sense to me, so what are they talking about?!