This is something I've always been curious about. Take a state like Michigan for example. The state has 5 safe Democratic seats, and probably around 5 marginal Republican seats. Why don't the Democratic incumbents help their colleagues more? Surely this would benefit them; more money and organizational power means a chance of more Democrats in the House, which means powerful positions on committees and favorable legislation. Why would John Conyers not dump thousands of dollars and volunteers into Tim Wahlberg's seat?