Voters across Maine, Nevada, South Carolina and North Dakota have cast their ballots in another day of primary elections in America. Much of the political world was focused on Maine’s high-stakes U.S. Senate contest even though the results weren't in question. Neither Republican incumbent Sen. Susan Collins nor Democratic challenger Graham Platner faced serious opposition for their party’s nomination. Elsewhere, President Donald Trump’s clout within his party was tested anew in states like South Carolina and Nevada, where he endorsed his favored candidates. Democrats hope to build momentum in Nevada in their broader push to reclaim key governor’s seats.