Anyone registered to vote can choose a Republican or Democratic ballot. Many of the people on the Democratic ballot (in my area) are running unopposed, so it was a good opportunity to try to get the least crazy people on the November ballot. Also, the republican ballot has 13 propositions that are not on the Democratic one, so that’s your only chance to have a say in those (and IMO they are really really bad!)
For the Texans specifically, I would like to add that Ken Paxton is trying to primary Presiding Judge Sharon Keller, Judge Barbara Hervey and Judge Michelle Slaughter of the Criminals Court of Appeals which is the highest level criminal appeals court in Texas. He is upset with them because they wouldn’t allow him to pursue voter fraud cases unilaterally, his office has to get permission from a local prosecutor now.
Ken Paxton has also put a lot of money into trying to primary state legislators who voted to impeach him, that is why so many incumbents do have challengers right now. Definitely look up your local races before going in to vote.
In case anyone is out of the loop on Attorney General Ken Paxton, I have one more link about the charges of securities fraud he was indicted on eight years ago. The case is finally going to trial in April.
