It would be a problem for the GOP at a presidential level for about 12 years until a recalibration but the GOP would have a massive Senate advantage.
Crucial difference being, I don't imagine ~70% of the population is going to tolerate ~30% of the population controlling ~70% of the Senate seats and stymieing their agenda into the 2040's. Rural white trash is going to have to experience a rather brutal lesson in democracy and economic/technological/military power.
How would this 70% fix this without amending the Constitution which requires 2/3 of all senators to vote for it?