The Texas voter ID law follows the following senario.
snip
Texas enacted in 2011 a strict photo voter ID law, replacing its existing non-strict,
non-photo ID law. It was implemented in 2013. On Oct. 9, 2014 a federal judge struck
it down; on Oct. 14, a federal appeals court re-instated the law on the basis that it
was too close to the general election to change the rules. On Oct. 18, the U.S. Supreme
Court affirmed that the law can be in effect for the November 2014 election. In
2015, a federal appeals court ruled that it cannot be enforced, sending it back to
the lower court. It is uncertain whether the law remains in effect, or whether an
earlier non-strict, non-photo law in place.
http://www.ncsl.org/research/elections-and-campaigns/voter-id.aspx
“Crawford v. Marion County Election Board”
“Crawford v. Marion County Election Board, 553 U.S. 181 (2008), is a United States Supreme Court case holding that an Indiana law requiring voters to provide photo IDs did not violate the Constitution of the United States.”
http://www.freerepublic.com/focus/chat/3351310/posts?page=27#27
Asking voters for ID cards is constitutionally legal as we see.