Texas law lets political parties set their own ballot access barriers for presidential primaries. For 2016, the Democratic rules let anyone on the ballot who pays $2,500. The Republican rules let anyone on who pays $5,000. See this story. Texas has been holding presidential primaries in every year starting in 1980. Democrats have always allowed qualification by fee. Republicans required a petition in the 1980’s but no longer do so.
In 2012, there were nine Republicans on the Texas presidential primary ballot, and four Democrats. The Texas 2012 presidential primary didn’t attract a great deal of attention because it was later than usual. It was held on May 29. Normally Texas primaries are in March, but the 2012 primary was delayed due to redistricting. It is possible the 2016 Texas primary will also be delayed, if federal courts require new districts.
In 2008, there were eleven choices on the Republican ballot and six on the Democratic ballot. The 2008 primary was March 4.