Nearly a third of U.S. counties will be left with just one insurance option next year on the ObamaCare exchanges, according to a new analysis fueling warnings about the impact of the insurance company exodus from markets across the country. The Kaiser Family Foundation study found residents in Pinal County, Ariz., are even at risk of having no insurance options on the exchanges, which provide subsidized plans. Republicans seized on the report Monday to claim that the health care overhaul is not providing the choices promised by President Obama and others. […] The Kaiser Family Foundation study found that overall,...