Congress could be hurtling toward a partial government shutdown as a December 7 deadline approaches — and as usual, President Donald Trump is to blame.

The House and the Senate still have to pass seven spending bills to fund multiple government agencies, including the Department of Homeland Security, the Department of Justice, and the State Department. But Trump has renewed a push for border wall funding, throwing a major wrench into these negotiations.

Senate Majority Leader Mitch McConnell had previously been optimistic about closing the year with little fanfare, but a veto threat over wall funding could make that tougher to do. Because these are spending bills that require 60 votes to pass, Democrats have a fair amount of leverage.

And they don’t appear to be backing down easily.

Senate Minority Leader Chuck Schumer signaled Tuesday that he would support no more than the already allocated $1.6 billion for funding a border fence and other security measures in the Senate version of spending legislation. Trump, meanwhile, is calling for $5 billion for the wall.

“They haven’t spent a penny of the $1.3 billion they requested in last year’s budget. … We’re not negotiating in the press,” Schumer told reporters. Democrats are also holding out over issues related to protecting the Mueller investigation and addressing the citizenship question on the census, matters they’d like to see tackled in the bill.

Senate Appropriations Chair Richard Shelby has characterized wall funding as the “linchpin” of current talks, telling reporters the $5 billion figure is a “red line” for Trump.

If Congress is unable to reach an agreement that gets closer to this figure, Trump indicated earlier this month that he could veto whatever bill comes across his desk.

Trump is refusing to negotiate on the wall, but he’s ready to blame Democrats for a shutdown

Trump’s central demand is much the same as it has been every time Congress has neared a similar deadline in past months: He’s insistent on getting more funding for the border wall, and he’s making his demand by pointing to the crisis at the US-Mexico border (which his administration fueled by closing off points of entry for asylum seekers).

Mexico should move the flag waving Migrants, many of whom are stone cold criminals, back to their countries. Do it by plane, do it by bus, do it anyway you want, but they are NOT coming into the U.S.A. We will close the Border permanently if need be. Congress, fund the WALL! — Donald J. Trump (@realDonaldTrump) November 26, 2018

“We will close the Border permanently if need be. Congress, fund the Wall!” Trump emphasized in a tweet on Monday, a post that followed a contentious weekend of US border action that included the use of tear gas on migrants attempting to seek asylum, the temporary closure of a border crossing near San Diego, and reports that asylum seekers would be required to remain in Mexico while filing their petitions.

A White House spokesperson did not immediately respond to a request for comment.

As Vox’s Tara Golshan has reported, this is far from the first time Trump has made wall funding — and himself — the primary focus in a possible shutdown fight. Trump has asked for anywhere from $5 billion to $25 billion to bolster this effort in the past even though a number of estimates have indicated that constructing the wall would actually cost much more.

In prior standoffs, Democrats have suggested that they’d be open to making certain concessions on a wall if they’re able to secure some legislative wins — such as a fix for the Deferred Action for Childhood Arrivals program — in return.

Senate Democrats have already chafed at adding any more funding to the proposed $1.6 billion allocation, which would go to a border fence and other security measures. “I think we’ve taken a position which is reasonable. We’ve given this administration more money than they can spend, and I don’t see it,” Sen. Dick Durbin (D-IL) told the Washington Post this month, when asked about upping the ante on such funds.

It’s not clear just how determined Trump is to secure this funding. He’s said he would veto a spending package that doesn’t include the money he wants, but this is far from the first time he’s touted such a claim.

It’s a threat he’s made — and caved on — before.

Some senators are making noise about protecting the Mueller investigation

Meanwhile, some senators are pushing a bill that would protect special counsel Robert Mueller and his investigation into Russian interference in the election, though it remains to be seen whether enough Republicans will support this.

Sen. Jeff Flake (R-AZ), who is retiring, has threatened not to vote for any of Trump’s judicial nominees until the bill is given a vote on the floor. Democrats are angling to add it as a rider to the final spending package.

“We Democrats, House and Senate, will attempt to add to must-pass legislation, in this case the spending bill, legislation that would prevent [Acting Attorney General] Whitaker from interfering with the Mueller investigation,” Schumer has previously said. Such a proposal would ensure that Mueller could only be fired by a Senate-confirmed DOJ official and give Mueller the ability to challenge his firing.

A bipartisan bill putting in many of these safeguards has already been approved by the Senate Judiciary Committee, though it’s since been shot down by Senate Majority Leader Mitch McConnell.

McConnell’s opposition, coupled with Trump’s likely negative response to such a measure, makes it unlikely this proposal will get approved. But spending negotiations give Democrats a broader platform to highlight the issue.

Democrats also want the Trump administration to drop the citizenship question from the census

Democrats have also fiercely opposed the addition of a new citizenship question to the US Census, which would ask anyone completing the survey to indicate whether or not they’re a US citizen. A spending showdown could be their opportunity to curb such efforts.

The addition of the question was first announced by Commerce Secretary Wilbur Ross this March, and he’s since argued that its inclusion would better enable the government to implement the Voting Rights Act. Democrats, however, say that such an inquiry could scare off immigrants who are frightened of answering this question and lead to inaccurate Census data as a result.

More than 20 states and cities have since sued the Commerce Department to eliminate the proposed question, and the Supreme Court is due to hear arguments early next year about the kind of evidence that can be used in the case.

Democrats are seeking the removal of the proposed census question as negotiations continue on the spending bills. The Trump administration, meanwhile, has steadfastly defended the question as it continues to face pushback in the courts.

As talks continue, the fates of all three major sticking points remain very much up in the air.

Clarification: A previous version of the story stated that the $1.6 billion funding figure Schumer referenced was for a border wall. It has been updated to reflect that this funding is for other border security measures.