Yougov is one of the better polls. Better methods than Ras, which calls zero cell numbers, only landlines.
But neither have any possibility of any sort to produce accurate results because the Obama administration sabataged the program which formerly restricted cold calls from sales people.
Consequently (by the time of the 2016 primaries) a sizable (and growing) segment of the populace had adopted a policy of not answering any calls from numbers not on their contact lists.
Pollsters cannot get any response at all from a sizable percentage of the electorate. So how accurate can they get with limited data?