And yet, Republican officeholders would rather cross the voters than cross Trump, even as the bottom is falling out on the numbers. Take Sen. John Cornyn, who’s up for re-election next year. Cornyn has complained about the damage being done by the shutdown, saying that it’s “Outrageous that federal prosecutors at Department of Justice and investigators at FBI, who we depend on to enforce the law are missing paychecks because of shutdown.” Yet after years of expressing scepticism about the efficacy of a border wall, he tells the Washington Post that he now won’t vote for a bill to reopen government without wall funding because, he said, “the president won’t sign it.”

For his part, Majority Leader Mitch McConnell (also up for reelection next year) could put spending bills that have passed the House—which would open all shuttered agencies except the Department of Homeland Security while negotiations continue—up for a vote on the Senate floor. But since the bills might pass, embarrassing Trump and risking a presidential veto, he won’t.

What’s driving this partisan unity is not ideological solidarity, but fear. So far only Senators Lisa Murkowski, Cory Gardner, and Susan Collins (the last two of whom are up for reelection in states Hillary Clinton won) have advocated for reopening the government before negotiating on a wall. When Murkowski was asked by the Post if she believed her GOP colleagues were afraid of the president she replied, “I think some are, absolutely.”