What to watch: Nevada has not had a Democratic governor since 1999, but this year, with Gov. Brian Sandoval barred by term limits, the race is expected to be very competitive. Six Democrats are running, foremost among them Christina Giunchigliani and Steve Sisolak, both Clark County commissioners. A recent poll showed them separated by just three percentage points, with a margin of error of four percentage points. On the Republican side, polls show Attorney General Adam Laxalt as the front-runner. Read more

There is also a House race worth watching in the Third District, which Representative Jacky Rosen, a Democrat, is vacating to run for the Senate. It’s a traditional swing district and has crowded primary fields on both sides.

The Senate race is expected to be one of the most competitive in November, but the primaries are quiet. Ms. Rosen and Senator Dean Heller, a Republican, are expected to easily win their respective nominations.

— MAGGIE ASTOR