The state of Nevada is one swing state that was a bright spot for Democrats last year: not only did Hillary Clinton carry the sate 48-46%, but Democrat Catherine Cortez Masto (by a 47-45% margin) was able to keep the seat of former Senate Majority Leader Harry Reid in Democratic hands. In addition to those two narrow victories, Democrats picked up two U.S. House seats (winning three out of four seats) and retook control of the state legislature.
Since the other U.S. Senate seat is up next year, those Democratic victories would seem to imperil the re-election chances of Republican Dean Heller, particularly since he was only elected to a full term in 2012 by a narrow 46-45% margin. However, Senator Heller has more immediate problems: he has a substantial primary opponent (Danny Tarkanian, who is the son of former UNLV basketball coach Jerry Tarkanian), and Nevada is a “closed primary” state, meaning that only registered Republicans (and registered Democrats, for that matter) can vote in their respective party primaries.
JMC recently polled this primary race (the poll can be viewed here), and the poll shows that while the Nevada race is one of two races (Arizona is the other) that could determine partisan control of the U.S. Senate, Senator Heller has more immediate things to worry about, such as getting the Republicans to renominate him.