In the pdf link, they list party affiliation raw numbers as 434/346/252 (D/R/I). That works out to (42.05%/33.53%/24.42%). Not quite 18% more D than R, but still way oversampling democrats.
This is truly a stealth poll that the media is using to suppress Trump supporters.
Ignore the polls and vote!
And considerably undersampling independents.
Also check out the conservative/moderate/liberal split. 384 moderates, 328 liberals and 320 conservatives. That has never been the ratio for any real recent election.