Primaries in four states on Tuesday will offer clues about how much tolerance voters have for candidates embroiled in controversies, while testing President Donald Trump’s sway in a crowded Republican primary and setting up a key race for governor in one of the country’s premier presidential battleground states.

Lindsey Graham, Nancy Mace and Graham Platner headline this week's primary elections to watch.

Four states - Maine, Nevada, South Carolina and North Dakota - are holding primaries ahead of November's midterms.