What to watch in Tuesday’s primaries as Graham Platner tries to clinch Senate nomination in Maine

Voters across Maine, Nevada, South Carolina and North Dakota head to the polls for another day of primary elections in America. But much of the political world will be focused on Maine’s high-stakes U.S. Senate contest. The results are not in question. Neither Republican incumbent Sen. Susan Collins nor Democratic challenger Graham Platner faces serious opposition for their party’s nomination. But Tuesday still marks a big moment for Platner, the embattled veteran and oyster farmer, who's fighti...