Absolutely the enthusiasm gap makes a huge difference. I know that 92% of Republicans are highly enthusiastic to vote compared to 60’s in the mid terms. That’s HUGE!
I remember the moment what little enthusiasm I had for McCain died. He looked right into the camera and told America that we have nothing to fear in an Obama Presidency. I looked at my (then) wife and said, “that man just lost the election”.
Where’s the “Not this BS again” guy?
Of course there is no great enthusiasm out there FOR Biden. There is great enthusiasm among us FOR Trump.
That “gap” is meaningless because there is as much or more enthusiasm AGAINST TRUMP.
By asking the wrong question — “How enthusiastic are you to vote for Joe Biden?” rather than “How enthusiastic are you to vote AGAINST Donald Trump?” — you get the misleading (to be highly charitable) result.