They do. But we have seen what happens to people who don't support the Dems. They are harassed, abused, their employers are targeted, they face knowing people will come after them.
Perhaps people are too scared to admit they don't support them, and are keeping their intentions and beliefs quiet and private,and will use the privacy of the ballot booth to express their views?
We have seen the same thing in the UK over the last decade, with it becoming worse since 2016. And in 2016 in the USA people firmly believed no way could trump win. It wasn't going to happen! After all, polls showed he wouldn't,right??
Question the polls in the same way you do the regular media. From the top, the people running them are bent,from the bottom, the electorate are too scared to be honest.
Take heart, fren. The polls lie and people lie and often for good reason, to ensure their safety.