This chart reflects the results of the new University of Texas at Tyler Poll -- done between October 15th and 28th of 1,033 registered Texas voters (905 likely voters). The margin of error for the registered voters is 3.03 points and for the likely voters is 3.26 points.
It shows the difference between Cruz and O'Rourke is lies than 5 points among both registered and likely voters.
Making these numbers more interesting is the fact that significantly more Republicans and Trump voters were questioned than Democrats and Clinton voters. It looks like some Republicans are crossing over and voting against Cruz.
