5. Nevada (Open): Nevada Democrats have found electoral success when the rest of their party struggled. Voters here went Democratic down the ballot in 2016. This time, term-limited Gov. Brian Sandoval (R) is one of the most popular politicians in the state, and he has so far declined to offer his endorsement to the front-running Republican, Attorney General Adam Laxalt. A potential front-runner on the Democratic side is Clark County Commissioner Steve Sisolak, a well-known figure in the Las Vegas area.