In the five or so years since hedge fund manager Donald Sussman and Rep. Chellie Pingree, D-Maine, have known each other, the investment tycoon has made his mark in her state, becoming its top political donor in 2012 and a major backer to Democratic super PACs. He's also found ways to bankroll her campaign, while buying a controlling interest in the local papers that cover her district.

Sussman, the billionaire manager of boutique hedge funds which manage about $8 billion in assets, married Pingree in 2011. She's the former president of campaign finance watchdog Common Cause. In his ...