On April 30, Maine’s Democratic Gov. Janet Mills dropped out of the race for a U.S. Senate seat. In a statement about suspending her campaign, Mills was blunt: “While I have the drive and passion, commitment and experience, and above all else—the fight—to continue on, I very simply do not have the one thing that political campaigns unfortunately require today: the financial resources.” As Mills said, financial resources matter in today’s political environment as campaigns grow more expensive each cycle. First-quarter financial reports filed in April with the Federal Election Commission (FEC) show where some of that money is going—and where it is not....