A theory
I think concrete signifies agreement to a certain plan. They are all concurring with it.
If I had to guess what they will do, my guess is that they will rally up antifa to make havoc at the polling booths. Probably antifa will be disguised as a false flag of some sort.
Then once they lose, they will say Trump violence prevented people from voting and that is why the dems lost. Therefore, they will reason, the election results are invalid.