Representative Dana Rohrabacher, a Republican fixture in California who represented Orange County for 15 terms, has lost his bid for re-election. His defeat underlines the party’s setbacks in a part of the state that was long a symbol of its political dominance. The Associated Press called the race on Saturday, with Harley Rouda receiving 52 percent of the vote to Mr. Rohrabacher’s 48 percent. Mr. Rouda, 56, is a former Republican turned Democrat who became a symbol of the Democratic efforts to win back Congress this year. Mr. Rohrabacher, 71, was viewed as particularly vulnerable because he defended Russia in...