Either conservatives have started lying to pollsters about their voting intentions or conservative officials started manipulating the vote totals in their favor.
Take your pick as to which possible explanation is most palatable and/or most probable.
But that would start costing them elections, so instead they coddle and abet the worst of them.
What do you call 9 people staying quiet when a tenth is being blatantly racist? Ten racists. Take it from me, I saw it in action growing up white in Mississippi.
If you don't have a representative sample of the population your poll will be inaccurate.
Do you have any reason to believe that pollsters and other statisticians are so ignorant of their own field not to understand this?
So they think they have a representative sample, but they really don't.
It can be explained simply by pollsters mainly living in large cities, and not really understanding rural Americans.