Special counsel Robert Mueller is expected to submit his long-awaited report on the Trump-Russia investigation to the Department of Justice soon. And House Democrats really, really want it to be made public.

In a rare bipartisan vote, the House of Representatives overwhelmingly passed a nonbinding resolution Thursday to do just that. Republicans joined Democrats in a 420-0 vote to approve the resolution, with just four lawmakers declining to take a stance by voting ‘present.’

It’s unclear whether Senate Majority Leader Mitch McConnell will pick it up. He blocked a similar bipartisan bill from Sens. Chuck Grassley (R-IA) and Richard Blumenthal (D-CT) from the Senate floor earlier this year.

The House, on the other hand, is intent on passing a resolution to make the report public because they’re not sure how much recourse they’ll otherwise have if the Justice Department decides to keep Mueller’s report under wraps.

The man who has the final say on how much of the report is released is new Attorney General William Barr, who hasn’t committed to making the report public, exactly, but insists he will follow the obligations put on him under law. When Mueller’s investigation concludes, Barr will have to give senior members of the House and Senate Judiciary committees some limited information, including why Mueller’s inquiry is wrapping up now. But Barr doesn’t have to disclose the full report under law.

Given the potential weight of Mueller’s report, Democrats and Republicans in the House want Congress and the American public to see the whole thing. Though McConnell has expressed support for the Mueller report’s release, he’s been fairly deferential to the Justice Department.

It’s possible Mueller’s report won’t implicate President Trump, in which case Republicans would also have a strong interest in making it public. But top Democrats on House committees charged with investigating the president are particularly eager to see if Mueller’s finding will open up new lines of inquiry for them.

“There may be some areas where, because of the limitations of his jurisdiction, that he had to stop. I don’t know what those areas would be,” said House Oversight Committee Chair Elijah Cummings (D-MD). “A lot of it may corroborate some of the things we’ve already found, which is helpful. But we’ve got a lot more work to do with regard to Russia’s efforts to interfere with our elections.”

How much information does Barr have to release about the Mueller report, and what can Congress do about it?

There are a few Justice Department regulations Barr will be looking to when deciding whether to release the Mueller report. These regulations were instituted in 1999, in large part a response to then-independent counsel Ken Starr’s bombshell report on President Bill Clinton and White House intern Monica Lewinsky, and they could help shield Trump.

These regulations specify that Barr needs to brief the top Democrats and Republicans on the House and Senate Judiciary committees on why Mueller’s investigation is concluding now. But they give Barr pretty wide leeway to decide how much information in the report to disclose, saying he can release information that he determines is in the public interest.

Democrats have been arguing strongly that the public release of Mueller’s report is in the public interest.

“As the Department of Justice made clear over the last two years, DOJ policy permits disclosure of investigative materials when it serves the public interest, even as they pertain to ‘uncharged third parties,’” a statement from Democratic Committee chairs including Cummings, House Judiciary Committee Chair Jerry Nadler (D-NY), and House Intelligence Chair Adam Schiff (D-CA) reads. “The public is clearly served by transparency with respect to any investigation that could implicate or exonerate the President and his campaign.”

The other thing Barr will have to keep in mind is a longstanding Justice Department practice to not publish negative information about a subject under investigation if that person hasn’t been charged with a crime. That protocol has certainly been broken in the past, but it could give Barr cover to explain why he’s not releasing the report.

House Democrats are trying to prepare for this scenario. A resolution to urge Barr to release the Mueller report to Congress and the public ramps up the pressure on the Justice Department.

If the resolution goes nowhere because McConnell declines to bring it up in the Senate, House Democrats have some recourse by trying to subpoena the report or get Mueller to Capitol Hill to testify. But they are already aware that could take much longer if the Trump administration fights it.

“I think we do have the ability to subpoena the underlying evidence; we can even subpoena Bob Mueller,” said Rep. Raja Krishnamoorthi (D-IL), a member of the House Oversight and House Intelligence committees. “But the time that it will take, because I think they will object and maybe force us into litigation, means there will be delay.”

Krishnamoorthi said he’s not yet aware of any effort in either committee to subpoena Mueller or his report.

“But I can bet you that if that report is not turned over and the evidence is not turned over there will definitely be a push for that,” he said.

Top Democrats have been tight-lipped about impeachment until they see Mueller’s report

In recent days, House Speaker Nancy Pelosi has reiterated that she thinks impeaching Trump is a futile business.

“Impeachment is so divisive to the country that unless there’s something so compelling and overwhelming and bipartisan, I don’t think we should go down that path, because it divides the country. And he’s just not worth it,” Pelosi told the Washington Post Magazine’s Joe Heim in an interview.

Pelosi has been walking this line for a while, making clear the House will conduct numerous investigations of Trump before it makes a judgment about whether to impeach the president. But she and other Democrats are also waiting to see whether the Mueller report contains a true bombshell, and if it’s just worth further investigation — or impeachment.

“What I’ve been saying all along is consistent with what she said,” House Majority Leader Steny Hoyer (D-MD) told reporters this week, referring to Pelosi. “She said we need to wait for the Mueller report, we need to see what the facts are. I think we need to have as much information as possible.”

It’s too early to tell if the Mueller report will change Pelosi’s mind. But we still don’t know if she’ll even get to see the whole thing.