For the first time in a long time, the Republican and Democratic leaders of the Senate began the week with messages of hope and bipartisanship.

Senate Majority Leader Mitch McConnell (R-KY) had made good on his promise to kick off open-ended debate on an immigration bill that could shield so-called DREAMers from deportation and beef up border security. And the chamber seemed poised to start a thorough, if not tricky, legislative debate.

But just hours into the week, that optimism has faded, replaced with doubt: Doubt that lawmakers could find a starting point, doubt that anything could get finished by McConnell’s self-imposed Thursday deadline, and doubt that any legislation currently on the table could get the requisite 60 votes to pass. By Tuesday afternoon, with the clock ticking, lawmakers were unsure when the first vote would even occur.

“I’m beginning to doubt the seriousness of some people’s desire to get a solution,” Senate Majority Whip John Cornyn (R-TX) told The Daily Beast.

The first signs that the entire process was screeching to a halt came shortly after McConnell’s remarks on Tuesday—when Republican leaders offered an amendment by Sen. Pat Toomey (R-PA) that addressed so-called “sanctuary” cities, which do not offer full help to the federal government for immigration enforcement.

Democrats objected because the amendment did not address the fate of DREAMers, those undocumented immigrants who were brought to the U.S. as children. Instead, led by Senate Minority Leader Chuck Schumer (D-N.Y.), they asked that the Senate vote first on each of the immigration plans that have been introduced, some of which have been crafted only by Republicans, and others that have bipartisan support.

Just like that, the chamber was at a standstill.

Republicans decried what they considered to be a delay tactic on a debate that Democrats had demanded as a pre-condition for ending a government shutdown last month.

“I’m not sure why you would block even moving to the initial consideration of amendments, which is what the Democrats are currently doing,” Sen. John Thune (R-S.D.) said. “That makes no sense if you’re the ones who have been advocating for literally weeks that we need to get on to an immigration bill.”

The failure to even start the debate without acrimony underscored the political volatility that has come to surround the topic of immigration reform in the modern political age. Other administrations have tried, and failed, to pass comprehensive packages before. But under Trump, the stakes are remarkably high, with lawmakers tasked with finding a resolution to the Deferred Action for Childhood Arrivals (DACA) program before it expires on March 5—a deadline that could be extended by the courts.

Progress was always going to be difficult. Tuesday showed that it could be glacial at best. Senators from both sides of the aisle were skeptical that any of the immigration bills in the Senate—of which there are at least five—could get the necessary 60 votes.

“No,” said Sen. Roy Blunt (R-MO), when asked whether any of the current pieces of legislation could meet the threshold.

Time isn’t on their side. McConnell declared on Tuesday that the Senate should wrap up its work on the issue by Thursday.

“What do they call us, the most deliberative body?” Sen. Bob Corker (R-TN) quipped. “We’ve been planning this for a long time. There was a government shutdown over this. So I hope we resolve it.”

The situation is so dire that Sen. Jeff Flake (R-AZ), eager to get to a solution, began crafting his own plan that incorporates much, but not all, of Trump’s immigration framework. On Tuesday, Flake hinted that the Senate was prepared to focus on whatever proposal could win over 60 votes—no matter what the president would sign.

“He has his framework already out there. That’s informed the discussion. But we need to work this out ourselves,” Flake said.

That could mean leaving out some of Trump’s immigration priorities in a final Senate-passed bill. As written, the legislation that mirrors the White House plan isn’t likely to win over Democratic votes—which would be necessary in order to get to 60—and would also scare off some GOP moderates like Flake.

Republican leaders began acknowledging weeks ago the likelihood that addressing Trump’s demand of ending so-called chain migration and the diversity visa lottery system would complicate efforts to pass a bipartisan bill in the Senate. But if the Senate’s final product does not include those two key White House priorities, House Speaker Paul Ryan (R-WI) is unlikely to bring it up for a vote in his chamber, where a majority of Republicans have already backed a version of Trump’s plan.

Cornyn, who is co-sponsoring the Senate bill based off of Trump’s framework, acknowledged that the Senate might have to chart its own course—even if the outcome can’t pass muster with the House or the president.

“The president has said what he wants. And we’ll see what’s feasible. I guess we all have to reconcile ourselves to the difference between what we want and what’s actually possible,” Cornyn said.

Amid the standstill, Sen. John Kennedy (R-LA) said he and his colleagues should stay in town and work toward a solution for as long as it takes.

“Most Americans work five days a week, and when they have a deadline they work through it,” he quipped. “You can tape the Olympics and go back and watch it.”