It can also depend on where you are and who you know. The groups are not evenly spread through society. In the UK and one side in politics dominates all my social circles - colleagues, people I went to school with, people I meet locally (to be fair, that does depend on what you do and who you meet - but I tend to "cultural" activities), people who share stuff on FB that I know (as opposed to the stuff in the feed - is which often ridiculously extreme both ways).

it might not be true, and surveys and voting patterns say otherwise, but it can definitely feel like one side is dominant. It can definitely be true that a particular place/activity/group is dominated by one side, which is what GP seems to be claiming, rather than that the US in general has shifted to the left?