TRAIN WRECK UPDATE: Minnesota’s Biggest Obamacare Insurer Leaves Exchange. “PreferredOne was the least expensive insurer in the Minnesota’s state-run Obamacare exchange last year. It was also the most successful at signing up customers, capturing 59 percent of the state’s market for private plans, according to CBS Minnesota. And now it’s leaving the exchange, and the 30,000 people who had enrolled in its coverage.”