https://mediadc.brightspotcdn.com/dims4/default/17729b9/2147483647/strip/true/crop/1500x788+0+83/resize/1200x630!/quality/90/?url=https%3A%2F%2Fmediadc.brightspotcdn.com%2F88%2F1b%2F023fd348480169c61b45cbc20f31%2F389b9fe7b9c46232291f0138828d2854.jpg washingtonexaminer.com joaquin castro 'all but certain' to challenge john cornyn for us 2019-03-16 Joaquin Castro, 48, who is beginning his fourth term as part of Texas in U.S. ..…