Despite failing to obtain funding from Mexico, Donald Trump still wants to build a wall along America’s southern border. Unfortunately for Trump, said fence costs billions of dollars and at present, no one is willing to give him the money. (Where’s Deutsche Bank when you need them?) As a result, Trump has turned to the familiar politics of hostage-taking in an attempt to secure the $1.6 billion he wants to begin construction. “If we have to close down our government, we’re building that wall,” Trump said during a rally in Phoenix this week, suggesting that he would not sign a spending bill to keep the government running—due by the end of next month—unless Congress ponies up. “One way or the other, we’re going to get that wall.”

Trump has made similar threats before, and failed to follow through. But the president is in a worse-than-usual mood these days, given his feuds with America’s C.E.O.s, his falling-out with Mitch McConnell, and his legal troubles at the hands of special counsel Robert Mueller. And according to both Wall Street and members of his own party, the chances of a political crisis this fall are pretty high.

Axios reports that even before Tuesday night’s campaign-style rally, Goldman Sachs had raised its odds of a shutdown to 50-50. A top G.O.P. source put the chances as high as 75 percent, saying “the peculiar part is that almost everyone I talk to on the Hill agrees that it is more likely than not.” (The rising spread between late September and early October Treasury bills suggests investors, too, are getting jittery.) As Jonathan Swan notes, “the president is spoiling for a fight.” That’s not the disposition or emotional character Wall Street is looking for when a government shutdown is also intertwined with the politics of raising the debt ceiling, something Congress must do to avoid a potential worldwide financial panic. Per Bloomberg:

Conservatives in the Republican Study Committee and House Freedom Caucus are pushing for deep cuts to entitlement tied to the debt ceiling which moderates in the party are not prepared to vote in favor of. That means Republicans will likely need to assemble a bipartisan vote that includes Democrats, who have rejected the idea of attaching any conditions to a debt bill. This may leave GOP leaders deciding that the best way to build support for the debt increase is to pare it with the must-pass stopgap spending bill. If the two are attached, Trump’s veto threat becomes more significant, risking a partial shutdown Oct. 1 and a debt payments default shortly thereafter.

Trump administration officials, including Treasury Secretary Steve Mnuchin, have previously promised that it’s in everyone’s interest to pass a “clean” debt-ceiling hike. But with the president in one of his trademark pissy moods, a dangerous game of brinkmanship may be in the offing. “A partial government shutdown prompted by failure to pass appropriations is one thing; a threatened default is in a different galaxy,” said the Bipartisan Policy Center’s Steve Bell. And while Mitch McConnell claimed earlier this week that there is “zero chance” Congress doesn’t raise the debt limit, that was before the escalation of his feud with Trump, who devoted several minutes of his Tuesday night tirade to antagonizing the Senate majority leader and then went after him on Twitter Thursday morning:

Trump, presumably, is lashing out, in part, due to The New York Times reporting that McConnell has said privately he doesn’t think Trump will be able to turn around his presidency. With a debt-ceiling crisis, Trump might prove him right even sooner than he thinks.