That can be very misleading. If you take into consideration that people are stupid enough to buy the "class struggle BS" and usually the people who do are employees who tend to lean left because they believe the BS leftist politicians constantly repeat, you might discover that even though the 2/3 of the GDP is from Dem areas, that is because these are simply areas that have a high number of employees that vote Democrat and work for Republican business owners.
Without those Republican business owners, those employees wouldn't even have a job in the first place and that part of GDP would not even exist.
So the fact that 2/3 of the GDP are from Dem areas could be simply a consequence of the fact that you have a small number of republican business owners and a large number of democrat employees. So, in essence, since those employees can only work because of the courage of the republicans that opened their businesses. You should thank Republicans and not Democrats for it.
Observe that I'm not saying that is the case. I'm just saying that if you don't know the % of business owners/risk-takers (which are indeed the backbone of any economy) that are republican or democrat, there is no way you can actually prove what you wrote.