President Trump wants to avoid a disastrous vote curbing his national emergency for the southern border wall, and one option on the table was a potential deal with Senate Republicans. Lawmakers, however, weren’t sure if he’d hold up his end of the bargain, and now the deal looks dead.

Republican Senators are overthinking tomorrow’s vote on National Emergency. It is very simply Border Security/No Crime - Should not be thought of any other way. We have a MAJOR NATIONAL EMERGENCY at our Border and the People of our Country know it very well! — Donald J. Trump (@realDonaldTrump) March 13, 2019

In just one day, the Senate is expected to vote on blocking Trump’s national emergency. Already, four Republicans have said they are open to opposing the emergency — enough to ensure its passage — and Trump could be facing as many as 10 GOP defections. Trump has threatened to veto the legislation, but legal experts say congressional passage could still aid those challenging the president in court.

A group of Republican senators wanted to help Trump out and proposed a trade. In exchange for voting against a resolution that would terminate the national emergency, they asked for the White House’s support on a measure that would significantly limit the ability of any president — including Trump — to use emergencies in the future, The Hill’s Alexander Bolton reports.

This measure, as introduced by Sen. Mike Lee on Tuesday, would amend the National Emergencies Act of 1976, and it would get a vote sometime later this spring if an agreement were made. Currently, a president’s declaration of national emergency expires one year after it is imposed unless the commander in chief decides to renew it. Lee’s measure would amend the original bill so that national emergencies expire just 30 days after they are declared unless Congress approves an extension, effectively curbing the power of the executive branch to use them.

Though some Senate Republicans had signaled an openness to considering this arrangement, the president has told Lee he won’t back the measure, according to Politico’s Burgess Everett.

News:During today’s Senate GOP lunch, President Trump called Sen. Lee and told him he will not support the GOP’s effort to change emergency law, per three sources. That destroys another exit ramp from tomorrow’s disapproval vote — Burgess Everett (@burgessev) March 13, 2019

His support was something lawmakers had been uncertain of since proposing the deal. As of Tuesday, Vice President Mike Pence did not offer a clear commitment to the plan, Bolton reports. A source close to the White House had also told Politico that Trump wasn’t necessarily guaranteed to back a bill that could limit his executive powers. Additionally, while Republicans senators were interested in putting a strict limit on the National Emergencies Act, the White House reportedly wanted to have a little more leeway.

It’s far from the first time that Trump’s unpredictability on a subject has gotten in the way of policy negotiations. Since lawmakers don’t know where he actually stands, let alone if he’s going to stick with a proposal, it’s making it tougher and tougher for Congress to actually reach a deal with him.

Trump’s unpredictability makes deal-making impossible

One reason Republicans might be wary of this deal: Trump’s fickleness has burned them before.

It was just last December when Majority Leader Mitch McConnell, seemingly with positive signals from the White House, triumphantly pushed through a short-term funding bill aimed at staving off a government shutdown — only to have Trump suddenly refuse to sign it. Shortly after, the government went into its longest-ever shutdown.

When McConnell announced that Trump was planning to sign a funding bill to reopen the government and declare a national emergency at the same time, he appeared so eager to make his statement he inadvertently cut off fellow Republican Sen. Chuck Grassley as he was making a speech. As observers commented at the time, there was a potential reason McConnell was in such a rush: He wanted to get the announcement out there before Trump changed his mind.

Democrats have also dealt with Trump’s unreliable promises. Last winter, Senate Minority Leader Chuck Schumer worked on brokering an agreement with Trump that included the exchange of $25 billion for his border wall for a path to citizenship for DREAMERs, or undocumented immigrants who had come to the US as children. Democrats took heat for offering funds for the border wall at all, and Trump ultimately reneged on the proposal, leaving them to address the fallout.

“We’ve had limited success in dealing with this president,” Senate Minority Whip Dick Durbin (D-IL) has previously told Politico. “His word isn’t good. Within 48 hours he reverses himself. It’s very difficult to enter into a long-term agreement.”

As of now, the numbers still look stacked against the president’s national emergency.