Sen. Jeff Flake (R-AZ) has an idea to keep the government open and strike a deal on immigration: Stop focusing on President Donald Trump’s constantly fluctuating opinion.

Republican leaders promised Flake a vote on a bipartisan immigration deal by the end of January. He wants them to deliver on that promise.

Last week, Flake, along with Sens. Lindsey Graham (R-SC) and Dick Durbin (D-IL), proposed a bipartisan immigration agreement that would have offered permanent protections for those in the Deferred Action for Childhood Arrivals program (DACA), as well as fund border security and address the visa lottery program and “chain migration.”

But Trump and the White House, who have increasingly engaged with immigration hardliners on DACA, nixed the proposal, with the president’s now-infamous comments calling African countries “shitholes” (or “shithouses”) in a White House meeting. Since then, GOP leadership said they wouldn’t vote on a bill that the president didn’t support.

The new condition, however, has a Trump-shaped obstacle: No one, including Republican leaders, appears to know what Trump wants on immigration.

“I maintain the only way to find what the president supports is to put something on the floor and vote on it,” Flake told reporters on Thursday. “Because last week the president said he would support anything we passed, [and] then he wouldn’t. I don’t know where he is today, so why in the world should the Senate be bound to what the president may or may not want?”

Here are Flake’s comments in full:

I had a commitment to have a DACA vote on the floor — bipartisan DACA vote on the floor — by the end of January. Then all of a sudden the condition was put on of if the president supports it. We don’t know what the president supports. I maintain the only way to find what the president supports is to put something on the floor and vote on it. Because last week the president said he would support anything we passed, [and] then he wouldn’t. I don’t know where he is today, so why in the world should the Senate be bound to what the president may or may not want? You put a bill on his desk and see if he signs it or not. Often, normally, if we are functioning here, we pass something and then say, “President, sign it or veto it,” instead of saying, “We are not going to do anything until we know.” I’m not inclined to vote for a CR. The Democrats have offered to go for a CR for a couple days to give us time to actually come together on these issues. That’s the right approach. We won’t be any better on the 16th of February as we will be next week. So let’s move it for a couple days.

Congress is barreling toward a government shutdown at midnight on Friday, January 19, if they don’t come to a spending agreement. Democrats, who have grown increasingly frustrated with Republican leaders’ slow-walk of immigration negotiations, have vowed to shut down the government if an immigration deal isn’t met with urgency.

Flake, who has always had a rocky relationship with the president, and announced his retirement with a scathing speech about Trump’s administration on the Senate floor, has joined Democrats in that stand.

At this point, it’s not clear that a couple more days of negotiations could resolve what has become an anarchic congressional debate over immigration. Trump spun negotiations into chaos last week, and has continued to engage hardline immigration hawks, who are unwilling to compromise with Democrats.

But that hasn’t deterred Flake and Graham from building up support for their bipartisan bill.