When he deferred to Beto for the 2018 Senate race, Castro lost much political clout. I can see him deferring again to Beto in 2020. People in TX still have “Beto-mania”, and it is incurable.
Dems are not going to put a Hispanic on the 2020 ticket. The last thing they want to talk about is the border and immigration. My money is on O’Roarke/Gillum ticket. That covers the soccer mom and black vote demos. Also sets up a generational contest between Gen X and a senior citizen POTUS.