There's nothing illegal about what he did.
Texas voter registration records are public data, as are participation in elections. Where you voted is recorded (just not who you voted for), and is available through the public voter registration records.
Nowhere on his flyer did he claim to be any kind of government official, working in any official capacity, or working on behalf of the state. Fraud is going to be hard to sell to a jury.
If you take the time to read any of the articles about it, the District Attorney doesn't say anything about this being illegal (because it isn't).