Is it? Your complaint is that things you disagree with are appearing more frequently, which they do when people upvote them. Sorry most of us have similar feelings about not voting / voting third party, but the only reason you’d call it astroturfing is if you think it’s disingenuous.
Astroturfing is when there is a disingenuous coordinated campaign with a goal in mind. This post is specifically against not voting or voting third party, and you came here to complain about seeing too many things like this post. If your complaint was about seeing too many voting / politics memes in general, I imagine you would recognize what sub this is and what month it is.
I don’t believe you would be calling an abundance of voting related memes in a political memes sub this close to an election with no goal in mind “astroturfing” unless you didn’t know what the word meant. The obvious implication is that you believe there is a disingenuous coordinated campaign against voting third party or not voting. My point is that there doesn’t have to be. It’s more likely that many people, myself included, agree with the message of the political meme in the politics sub, and probably more than normal since we are so close to the election.