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.

Thirty-four seats in the U.S. Senate are up for election on Tuesday, putting the balance of power between Democrats and Republicans in question. Nineteen of the seats up for election are held by Democrats,

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.