The WG’s David Winston argues that it was mainly independents, not other demographic groups or party bases, which drove recent Democratic gains in Virginia, Alabama, and Wisconsin:
Is a blue wave about to hit the GOP head on? While a higher turnout usually favors Democrats as we saw in Virginia, Republicans have won key House and Senate races in high-turnout years. 2016 is a good example. However, Democrats don’t necessarily need a presidential year to win either, as we saw in 2006. But whatever the turnout this fall, both parties need independents to win.