Since taking office on January 20, Donald Trump has reversed his stance on scores of positions he held on the campaign trail and, in some cases, through his first several months in the White House. NATO? What was once “obsolete” is “no longer obsolete.” Federal Reserve chair Janet Yellen? When he was running for office, she was conspiring with Barack Obama to keep interest rates low and had good reason “to be ashamed of herself,“ but now? She’s fine and might even get another term. China? The country’s actually not a currency manipulator. The Ex-Im bank? It’s “actually a very good thing.” His Kremlin crush Vladimir Putin? Let’s just say that Vlad’s got a lot of work to do if he wants to be invited to Trump’s 71st birthday party this June. Bashar al-Assad? The dictator is no longer the Syrian people’s problem to deal with on their own. Eliminating the national debt, clocking in today at nearly $20 trillion? O.K. fine, that probably won’t happen. Goldman Sachs? During the campaign, association with the investment bank’s employees disqualified a person to hold the highest office in the land, but now that he’s thought about it, they actually make great senior advisers and Cabinet members.

One thing he hasn’t reversed course on, however, is immigration. Since taking office, Trump has drafted two travel bans (both suspended by federal courts), called for Customs and Border Protection and Immigration Customs Enforcement to hire 15,000 extra agents and, of course, has continued banging on about his ridiculous, costly border wall. Now, in what will be the ultimate test of the 45th president’s commitment to a boondoggle that is equal parts monument to his ego and mascot for his base, Trump may let the government shut down if he doesn’t get the wall-building funds he demands.

As of Saturday at 12:01 A.M., parts of the federal government will begin to shut down if Congress fails to come up with a spending bill that Republicans, Democrats, and Trump can agree on. That’s problematic since 1) many Republicans are reluctant to spend the more than $20 billion the wall is estimated to cost; 2) Democrats have said in no uncertain terms that they will absolutely not vote for any bill that funds the wall; and 3) Trump previously promised that Mexico, not the U.S. taxpayer, would pay for it. That, of course, is not the case. As former Mexican president Vincente Fox so memorably said, “when will you understand that I am not paying for that fucken wall. [sic] Be clear with US tax payers. They will pay for it.” (Over the weekend, Trump lamely insisted that Mexico pay the United States “eventually but at a later date so we can get started early ... in some form.”) And now Trump is threatening to hold his own government hostage if Congress doesn’t give him a wall that polls show few Americans and none of the lawmakers representing districts along the border wall want.

Although Republicans control both houses of Congress and some would reportedly be “willing to set aside funds for the border,” The Wall Street Journal notes that “many are reluctant to imperil a bill that would need at least eight Democratic votes to pass the Senate.” Plus, “G.O.P. leaders are also likely to need Democratic votes in the House, where some conservatives are expected to oppose the bill, giving Democrats unusual leverage at a time of full GOP government control.”

“The Democrats do not support the wall,” House Minority Leader Nancy Pelosi unsurprisingly said on Sunday. “The wall is, in my view, immoral, expensive, unwise, and when the president says, ‘Well, I promised a wall during my campaign,’ I don’t think he said he was going to pass billions of dollars of cost of the wall on to the taxpayer.”