In the waning days of her congressional race, Republican Katie Arrington attempted to paint her opponent as a one-issue candidate, concerned only with offshore drilling. The issue, however, is likely one of the main forces that helped Democrat Joe Cunningham turn the 1st Congressional District blue for the first time in four decades. And it may have resonated with an important constituency that Cunningham’s staunch opposition to fossil fuel exploration likely spoke to: conservation-minded conservatives. “It’s a huge group in the 1st District,” said outgoing Rep. Mark Sanford. Sanford, who lost to Trump loyalist Katie Arrington in a primary for...