Roy Moore has defeated Luther Strange in a Republican runoff for Senate seat, despite Strange having Donald Trump's endorsement. Moore, a Steve Bannon-backed right-wing firebrand who has said homosexuality should be illegal and Muslims should not be allowed to serve in the U.S. Congress, won by 9%.

What to watch for: Sen. Bob Corker, a mainstream Republican, announced his retirement today, and several other sitting Republicans are facing primary challengers from the right. As Strange said in his concession speech, "We're dealing with a political environment that I've never had any experience with."