Somewhere between 15-25% of Republicans disapprove of Trump's handling of the riots and might otherwise consider voting for a Democrat in a state race (hence why Ds were able to win in KY and LA).
A successful peal-off in a presidential election would give Democrats 40+ states
15-25% of Republicans are not voting for Biden BUT if they stay home that could flip several states
Look at the 2017 Alabama Senate race. Doug Jones got the same amount of votes Hillary Clinton got, but Roy Moore drastically underperformed Trump. Because Republicans stayed home.
If 5% of the Republicans stayed home in 2020, thats about 3.75 million people across the country. If equally to each state by population, that should flip FL, NC, TX, OH, and IW