If you want to follow the money - betting odds, this site is interesting
https://www.sportsbettingdime.com/polit ... tion-odds/
Scroll down to the "Changes in Win Probability Over Time" and play that over time. Republicans should be and are worried.
Personally I think the odds of of Mike Pence ending up being the Republican candidate at 26 to 1 might well be worth a punt. The chance of Trump dropping out I think is greater than 26:1, either as a result of contracting corona virus and being unfit to stand or out of pique. I might put a few bob on Pence as Republican candidate at those odds.