There are plenty of Republicans on Capitol Hill who aren’t fans of President Trump, to put it mildly. A handful have been outspoken about their differences with him, but most of these Republicans represent safe seats or weren’t facing reelection for a while. Some privately voice their concerns about the Trump White House, but pull their punches when talking to the press. Many take their signals from Republican leadership, trying to pretend that Trump isn’t even president by pivoting to other issues when asked about the endless self-inflicted controversies.

But no GOP elected official has challenged Trump like Arizona’s Sen. Jeff Flake, who is aggressively taking on the president and his own party’s fecklessness for supporting him in a book that’s coming out in the run-up to his reelection campaign. In an excerpt from the book, Flake equates the predicament that Republicans face with Trump to the life-destroying flood from the Bible. “If one is being honest, the flood becomes the thing that is most worthy of attention. At a certain point, it might be time to build an ark,” Flake writes.

This is highly unusual political behavior—the kind of risk-taking that most consultants would warn against. Facing the prospect of a credible primary challenge from a candidate with White House support, Flake is stirring up the Republican hornet’s nest even further.