The big picture: Tonight's primaries are all about governors

Governor LePage leaning over a podium
Maine Gov. LePage is term limited and there are 4 Republicans running to replace him. Photo: Gabe Souza/Portland Press Herald via Getty Images

Five states have primary elections today, bringing the nationwide total of states that have held primaries this cycle to 21.

What to watch: Keep your eyes on governor's races in Maine, Nevada and South Carolina, as Democrats are competing to replace their state's Republican chief executive. Both sides have been pouring record amounts of money into gubernatorial races across the country.