AUSTIN, Texas (Reuters) - Texas should be playing a role in Republican politics this year as big as, well, Texas. The fast-growing state - the most populous by far in the Republican column - has four new seats in the U.S. House of Representatives, a big U.S. Senate race and more than a 10th of the delegates who will choose the party's presidential nominee. But a racially tinged dispute over redrawing its congressional districts has delayed the Texas primary by almost three months, complicated the U.S. Senate and House contests and altered the race for the White House. ...