Primary races to watch in Nevada, South Carolina, Maine

Primaries in different parts of the country on Tuesday could exert some influence on Republicans' chances at gaining back ground from Democrats in November and help decide whether an often unpredictable House Republican who has upset members of her own party will make it to the general election. Here are a few races to watch:

Republicans will pick their Senate nominee to try and defeat Democratic incumbent Sen. Jacky Rosen this fall.