Incumbent Republican Sen. Ted Cruz and Democratic challenger Colin Allred's Senate race is among the most closely watched this election cycle.

FORT WORTH, Texas (AP) — Republican Sen. Ted Cruz, of Texas, sought to fend off an underdog challenge Tuesday from Democratic Rep. Colin Allred in one of the year's most expensive races, which is testing shifts in America's biggest red state and could factor into the fight for U.S. Senate control.

The race that could determine who controls the U.S. Senate. An Allred victory would give Texas its first Black senator and boost the Democrats' chances of maintaining their narrow Senate majority. Cruz winning would mean a third term for the incumbent Republican.