> Saying party X plans to do something

but that's not the whole thing being said.

Party X may have been planning on something, but party Y threw a wrench in the middle, causing party X to have to make some response. By implication, party X believes party Y to be throwing a wrench, hence, party X must act. Therefore, party Y also must be planning something that counteracts party X's desires. If it weren't so, party X would not act (as that costs money).

The thing that contradicts Party X's desires can just be not doing the thing Party X wants done, it doesn't have to be doing an equal and opposite thing.

This seems like a variation on the fallacy of the excluded middle.

It's closer to so-far-unnamed fallacy of "the right has no agency." Everything they do is in response to something done by the democrats or the left or whatever and so they aren't responsible for their actions.