While he survived a brutal and controversial Senate primary in 2014, Thad Cochran of Mississippi, citing his failing health, is resigning effective April 1. A special election will be held to finish the remainder of his term that ends in 2020. If no one gets above 50 percent, a runoff will be held. For now, Gov. Phil Bryant will appoint an interim senator to fill the vacancy until the election. Cochran’s colleague, Sen. Roger Wicker (R-MI), is up for re-election this year and is facing a challenge by state Sen. Chris McDaniel. McDaniel challenged Cochran in 2014 (via NPR): I...