If Republicans lose 2020, 2024, and maybe 2028 they will have no choice but to change strategy. Personally I don't see it happen. McConnell has appointed people onto the court like crazy for a reason.
There are still many tricks they can use to prevent this scenario from happening. They can purge voter rolls, limit early voting, reduce the number of polling stations in urban areas. Implement tougher voter ID laws and close down DMVs in counties in the black belt and along the Rio Grande. Although a lot of that depends on if Roberts can repeal the VRA. If that is done I think if Republicans regain their supermajorities in TX, GA, and NC in a possible Biden midterm in 2022 then assuming they loose in 2024 they could possibly get a District Method plan on the ballot in a 2026 midterm. Assuming 2026 is in line with 2006 and 2014 they may be able to get majorities. This will essentially cut in half whatever Democrats win in TX and GA allowing them to go on the offensive in states like DE, CT, RI, and FL.
And what about the Senate?
Don't the Democrats need to win the senate too, they have to change their strategies too.
Republicans have a long history of under performing in the Senate compared to expectations and this has allowed the Democrats to get and keep majorities they should not have been able to hold. Part of this is precisely because of the Republican agenda on things like health care. Trump can win Ohio by double digits on trade and then Sherrod Brown can turn around and win it by emphasizing healthcare.
A local good ole boy running on Medicaid and minimum wage will do better then a Koch brothers backed shill in a Senate race even as the state is going hella Republican because of trade, immigration, abortion and/or guns.
