The frustrating thing is that if he hadn't ran in 2020 he would at the very least be treated as a much more serious challenger.
If he hadn't run in 2020, I could see O'Rourke holding Abbott to within 5%, given the polarizing policies which Abbott has enacted in the past few years. But instead, I'm expecting him to lose to Abbott by something similar to what Hegar lost by to Cornyn.
538's data is interesting, that Abbott's approval ratings have gone bad this year. Still, I doubt that's toxic enough to lose despite partisanship.