“People across this country — Republicans, independents, and Democrats — agree that our top priority has to be fighting corruption in Washington,” Massachusets Sen. Elizabeth Warren said in an ad broadcast thousands of times in Iowa ahead of the Feb. 3 caucuses. “I’m not doing big-dollar fundraisers. I’m not selling ambassadorships to donors. I’m not cozying up to super PACs.”

For rank-and-file Democrats, who take it as a matter of faith that “corrupt” campaign finance is the root of all evil in U.S. politics, this is a powerful message because recent history has proven that no amount of facts or evidence can dissuade them from this dogma.