Trump has thrown coronavirus relief into doubt. Here’s what could happen next.

Adding heft to his threat, on Wednesday Trump vetoed a defense bill that Congress approved by a large bipartisan margin and that has passed every year for nearly 60 years.

So, things are pretty chaotic right now. “This is unprecedented,” said Molly Reynolds, a congressional expert with the Brookings Institution, “because we generally wouldn’t expect a president to largely sit out negotiations of this level in Congress and then swoop in after both chambers have overwhelmingly passed the bill.”

Here are some scenarios for what could happen next. It’s not clear at this point which is most likely.

This turning out to be another Trump bluff is the cleanest way this could all end, and that’s the outcome congressional leaders prefer (even if Democrats are making some hay of it). Congress passed the spending/coronavirus-relief bill and the separate defense bill by veto-proof majorities, indicating they strongly want all this to be made law. The high likelihood of a veto override didn’t dissuade Trump from vetoing the defense bill, though.

He had been threatening a veto since the National Defense Authorization Act was passed without some unrelated provisions he wanted in it. Trump was less direct about the stimulus and spending bill — he didn’t explicitly threaten a veto, though that was the implication. His NDAA veto is probably headed for his first veto override when it goes back to Congress next week. Will he want to rack up two of those in the last week of his presidency by vetoing the spending bill?

There is a history of Trump backing down on veto threats. He teased he would veto a spending bill in 2018, then relented.

Trump’s main gripe Tuesday was that he wants stimulus checks to more than triple, from the $600 in the bill now for most Americans to $2,000. Democrats are down for that, even though amending the legislation this late in the game is going to be difficult if not impossible. House Speaker Nancy Pelosi (D-Calif.) is putting together a plan to get her chamber to approve $2,000 stimulus checks on Thursday. But since most lawmakers are gone for the Christmas holiday, she’s setting up the vote in such a way that if one Republican stays in Washington and objects, the $2,000 proposal will fail.

Given that, Pelosi’s attempt to capitalize on Trump’s curveball seems more political than substantial. Still, if Trump really wants to double down, he could by supporting Democrats’ vote. It would force Republicans who don’t approve of such expensive checks to directly contradict the president, which they are loath to do. Senate Republicans would all have to agree to the $2,000 stimulus checks, which is far-fetched given many of them already say the $900 billion bill they approved is too expensive.

If Trump sides with Democrats and Republicans object, we have a standoff. The ball would be in Trump’s court to persuade the rest of his party to go along with him — something he’s succeeded wildly at when it comes to, say, contesting his election loss. But he’s struggled to do this on legislation.

This would be one of Congress’s worst-case scenarios because it would do two things:

• Potentially set up a government shutdown, since the coronavirus relief legislation also funds the government through next fall. (Current government funding runs through Monday.)
• Force lawmakers to come back to Washington and override his veto to get the legislation passed. (Lawmakers will have to come back next week anyway to override his veto on the defense bill.) This scenario would force Republican lawmakers into an aggressive act of defiance against the president.

This is the more passive way Trump could reject the spending/virus-relief legislation, and it wouldn’t give Congress a chance to fight back.

The president has 10 days, excluding Sundays, to decide whether to sign or veto legislation. If he does nothing at the end of those 10 days, normally the bill becomes law. Unless Congress goes out of session. Lawmakers can easily keep Congress in an informal session to prevent this. But this Congress also officially ends on Jan. 3. Depending on when Trump officially receives the legislation, he could hold on to it until Jan. 3, do nothing and wait until a new Congress starts, making the old Congress’s legislation dead. (Fox News’s Chad Pergram has a detailed Twitter thread on how this works if you want to get into the weeds.)

So Trump has a chance to deny Congress the opportunity to come back and override his veto with a scenario that doesn’t even require him to veto it.

What this would be is not clear. But Trump in the past has taken loud, tough stands on public issues and then backed off when lawmakers talked to him behind the scenes.

This post has been updated.