Cruz is a former state solicitor general and tea party favorite who is vying with Sadler, a former state representative, in the Nov. 6 election to succeed retiring U.S. Sen. Kay Bailey Hutchison.
Friday's debate was mostly civil with neither side interrupting or clashing much verbally. It wasn't nearly as heated as the Oct. 1 debate when Sadler called Cruz a "troll."
Cruz has raised 10 times as much money as his opponent and only agreed to two debates, saying more would give Sadler free air time.
The winner of the election will replace retiring U.S. Sen. Kay Bailey Hutchison.