Maine is one of four states with primary voters going to the polls on Tuesday, and it has one of the most closely watched races in the country, as Democrat Graham Platner seeks to lock up the nomination to take on incumbent GOP Sen. Susan Collins despite his recent string of scandals. There are also primaries in South Carolina, Nevada and North Dakota. Here are the major races to watch: Maine Senate raceThe Senate race in Maine has been a priority for Democrats seeking to topple GOP Sen. Susan Collins in their quest to win back the upper chamber. Platner, a 41-year-old military veteran and oyster farmer, has seen surging support among Democrats in Maine, billing himself as a working class, anti-establishment candidate with a focus on opposing the "billionaire class."But new allegations against Platner emerged in the week before the primary, and it's not yet clear how or whether they will affect the race. Just over a week ago, the Wall Street Journal reported that Platner's wife told his campaign that he had sent sexually explicit text messages to other women soon after the couple got married in 2023. And last week, the New York Times reported on alleged "unsettling" behavior by Platner toward some women he dated, including one who described him as "toxic" and "abusive," particularly when he had been drinking. Platner has denied physical abuse and suggested the allegations are politically motivated. He has acknowledged struggling with PTSD and alcohol during what he called a "very dark period of my life."The developments followed other personal controversies, including problematic internet comments he made years ago, along with a tattoo he got during his time in the Marines that is widely recognized as a Nazi symbol. Platner has since apologized for the posts and covered up the tattoo.