The question becomes is which candidate will be able to pull in the most O'Rourke supporters? As for the senate, Cornyn isn't Cruz, he's more popular. Trump has a 50% approval rating in Texas, 45% disapprove so O'Rourke probably couldn't ride the anti-Trump vote to a win against Cornyn who is much more liked by Texan's as a whole than Cruz was. My opinion at this time anyway.
It's high past time that we start electing Americans to congress and the presidency who put America first instead of their political party. For way too long we have been electing Republicans and Democrats who happen to be Americans instead of Americans who happen to be Republicans and Democrats.