If “Fighting Bob” were alive today, he’d be howling in the Capitol. A hundred years before the Tea Parties, Senator Bob La Follette of Wisconsin was the original Republican insurgent. In the early 1900s, he led a grassroots revolt against the GOP establishment and pioneered the ferocious tactics that the Tea Parties use today—long-shot primary challenges, sensational filibusters, uncompromising ideology, and populist rhetoric. But there was a crucial difference between La Follette and today’s right-wing insurgents: “Fighting Bob” was a founding father of the progressive movement.

Read an excerpt from my new book, Unreasonable Men, at the Atlantic