Political analyst Charlie Cook today changed his race rating for the Texas Senate race to toss-up from "lean Republican." He also moved the race rating in West Virginia in favor of Democrats and the Montana race in favor of Republicans.

Why it matters: Republican Ted Cruz facing a serious challenge from Democrat Beto O'Rourke in Texas is yet another sign of the momentum building for a "blue wave" in November. Cruz and O’Rourke will face off in Dallas tonight for the first of three scheduled debates.