Sargent: Two Republican senators, Thom Tillis and Lisa Murkowski, have now called for the resignation of Homeland Security Secretary Kristi Noem. He lashed out at them as “losers” and “terrible senators.” But in truth, Noem’s tenure suddenly does look very shaky. A new review of the killing of Alex Pretti undercuts Noem’s initial account. It’s very clear this whole thing has gotten away from Trump and his advisers and has taken on a momentum that is now highly unpredictable. Well, Senators Thom Tillis and Lisa Murkowski both called for Noem to step down this week.