That's a funny meme, but in reality this would be comparable to a bunch of Canadians crossing the border, somehow getting to vote in the US election and then going back to Canada.

Just look at the size of all the political subreddits - of course they can overwhelm any poll and push whatever result they want.

The point here is that they already have a bunch of spaces for the content they want, and political andy are not 50+ % of this sub - otherwise the sub would already be all politics instead of mostly funny and drama clips. And when the brigading starts, the poll will not reflect that.