Let me dumb it down for you:
It doesn’t mean 71% of U.S. GDP comes from Democratic voters or that Democrats create most economic output — it simply reflects that the most economically productive counties (big cities and metro areas) tended to vote Democratic in that election.
It isn’t a measure of economic policy effectiveness — many other economic, geographic, and demographic factors influence where GDP is generated.
Large metropolitan counties with high economic output (financial centers, tech hubs, major service economies) overwhelmingly voted blue in 2020. Smaller, rural counties with relatively lower GDP tended to vote Republican. That leads to a big gap between number of counties and share of economic output.
Newer analyses using 2024 election results suggest that figure would be lower (around ~62%) because some populous, high-GDP counties shifted in 2024.
California Gov. Gavin Newsom said his state’s taxpayers give the federal government more than they receive in federal spending, while the situation in Texas is the opposite. Nonpartisan data backs him up.
www.politifact.com