by Joel Jacobs and Megan O’Matz ProPublica is a nonprofit newsroom that investigates abuses of power. Sign up for Dispatches, a newsletter that spotlights wrongdoing around the country, to receive our stories in your inbox every week. A decade ago, strange billboards started showing up, including in New York’s Times Square. They weren’t advertising a product. They were vilifying Connecticut’s then-governor, Dannel Malloy. And they could be…