Related and interesting podcast: https://podcasts.apple.com/us/podcast/search-engine/id1614253637.
According to what he found that is somewhat the way it works: two fake candidates and the one with more yard signs got way more votes. Doubt that generalizes to the US presidency though; especially with this election.
It looks like it comes specifically from composite wood and the glues used in making those composites, not solid wood. That seems to be supported by some quick internet searching. Regular wood appears to release formaldehyde at high temperatures.