I'm not the most perceptive person in the world, but I realized back in the 80s that the MSM were gaming polls - under-sampling Rs to get results they hoped would discourage Rs from voting, and then sampling more honestly in October for CYA. In 2016 Trump scared the MSM so badly they skipped the CYA part.
Consequently, IF the MSM are gaming their sampling like usual, what looks like a Blue Wave Fizzle might even turn out to be a Trump wavelet or wave. But there's just one poll to which I pay attention.