There is a subtle difference though because a vote is supposed to be a act of support. With the trolley problem there is nothing to support.

Voting for party A/B is a reward that encourages party A/B to do more of what they're doing.

So let's say only 1000 people voted because everyone else hated both options. That would pave a path for party C that would not exist if everyone held their nose and voted for crap.