Senate Democrats infuriated by President Donald Trump’s abrupt firing of FBI Director James Comey have begun weighing a “nuclear option” against Senate Republicans to try to force them to commit to an independent investigation of Trump’s ties to Russia — pulling a procedural move to halt all day-to-day activity in the Senate. In other words, going on a kind of strike.

Democrats are holding off on pulling the trigger — at least for now.

"I hope it doesn’t get there,” Sen. Dick Durbin (D-IL), the number two ranking Democrat, said in an interview on Wednesday when asked if Senate Democrats would try to essentially shut down the upper chamber of Congress. “I’m hoping for a bipartisan approach to this. But let’s wait and see.”

Here’s how Senate Democrats’ “nuclear option” over Comey would work: Unlike the House of Representatives, the Senate operates under what are called “unanimous consent” agreements. If Senate Democrats withhold their consent, the routine functioning of the body — from committee hearings to routine floor votes — could grind to an immediate halt.

“It would stop everything in the Senate and effectively shut it down,” said Josh Huder, a congressional scholar at Georgetown’s Government Affairs Institute. “If they go down this road, things could get pretty slow and ugly in the Senate.”

In several interviews Wednesday morning, Senate Democrats said they would not rule out taking this dramatic step to confront Republicans over Comey’s ouster. They did confirm that members of their caucus have discussed the measure — even if they haven’t decided yet if they want to go that far.

Already, at least three major progressive activist groups told Vox Wednesday that they are demanding Senate Democrats use every tool at their disposal, including this nuclear option, to force Republicans to cave on appointing a special prosecutor.

"There's no reason Donald Trump should be able to confirm nominees or pass laws while smashing the rule of law to pieces," said Ben Wikler, Washington director of MoveOn.org. "This is an in case of emergency, break the glass moment. Democrats should shut down the Senate until a special prosecutor is appointed.”

Democrats have moved to slow the Senate. How far will they go?

On Wednesday morning, Democrats did take one big step in the direction of slowing down Senate business over Comey’s firing. Sen. Dianne Feinstein of California invoked a rule that prevents committee hearings from going on for more than two hours after the Senate convenes. That effectively closed off all Senate committee business after noon on Wednesday, leading some Senate Republicans to voice their frustrations.

Sen. Susan Collins (R-ME) is on Senate floor saying she's upset scheduled hearing on senior care is being blocked by D's over Comey news — Benjy Sarlin (@BenjySarlin) May 10, 2017

Democrats have also begun saying that they won’t confirm Comey’s replacement without a guarantee of a more thorough investigation. "I think that we ought to frankly hold off on the FBI director until we get the special prosecutor,” Sen. Mark Warner of Virginia told Politico's Seung Min Kim on Wednesday.

Still, Democrats are a far cry from the most extreme steps they could take in response to Senate Majority Leader Mitch McConnell’s declaration that a special prosecutor is unnecessary. (Democrats have demanded that the White House either appoint a “special prosecutor” to investigate Trump’s ties to Russia or that Congress form of a bipartisan select commission to do so.)

The procedure for Democrats would be complicated and time-intensive. But as Adam Jentleson, Harry Reid’s former deputy chief of staff, wrote in January, Democrats have dozens of ways of binding McConnell’s hands should they choose to use them.

For instance, Senate Democrats could block McConnell on hundreds of decisions that are normally approved by unanimous consent without second thought — things like when the Senate will meet, minor and uncontroversial tweaks to legislation that doesn’t get written about in the press, and low-level presidential appointments that require Senate confirmation.

“All of the routine business of the Senate would stop,” said Huder, the Georgetown scholar. “Most of the things that happened in the Senate happen by unanimous consent, which is almost the exact opposite of the House.”

One key variable is that not every Senate Democrat needs to go along with the plan for it to work. “If a single senator objects to a consent agreement, McConnell, now majority leader, will be forced to resort to time-consuming procedural steps through the cloture process, which takes four days to confirm nominees and seven days to advance any piece of legislation,” Jentleson writes. “Since every Senate action requires the unanimous consent of members from all parties, everything it does is a leverage point for Democrats ... each of the 1,000-plus nominees requiring Senate confirmation — including President Trump’s Cabinet choices — can be delayed for four days each.”

So far, Democrats have given their consent for the Senate to proceed on votes for Trump’s executive branch appointments. But given that even scheduling times for these votes requires unanimous consent, Democrats have hundreds of unused opportunities to slow down the Senate, according to Huder.

Activists ratchet up calls for Democrats to deploy obstructionist tactics

On Wednesday morning, Senate Democrats convened in the Capitol for an emergency caucus-wide meeting to decide their response to the Comey firing. Before the meeting, Sen. Debbie Stabenow of Michigan said that this nuclear option over Senate procedures would be one of the things they’d discuss deploying in their reaction. After the meeting, Senate Democrats suggested that the option was on the table.

“I don’t think people will make a rash judgment about the right approach, but there is absolutely a consensus that we need to do whatever we can do [to get] an independent investigation,” Sen. Michael Bennet (D-CO) said.

Asked if that meant shutting down the Senate over Comey, Bennet demurred. “We’ll see. We’ll see,” he said. “This may be the most important thing we deal with here for a long time.”

Progressive activists are trying to push them to take the plunge. Murshed Zaheed, of the progressive advocacy network CREDO, said he was encouraged that Sen. Feinstein had closed down committee hearings on Wednesday and that Sen. Warner called for a delay in the FBI replacement until a special prosecutor was appointed.

“Those are steps in the right direction. But they need to shut all Senate proceedings down until there’s a special counsel. This is a constitutional crisis. This is code red time — Democrats need to shut the whole Senate down until there’s a special counsel,” Zaheed said.

Adam Green, of the Progressive Change Campaign Committee, added that it was reasonable for Democrats to try shutting down the Senate over the Comey investigation.

“What is a proportionate response to a constitution crisis? It’s hard to imagine something being too extreme,” Green said. “It can’t be ho-hum. Democrats need a very strong response to make clear that this cannot happen.”

And the new left-wing group “All of Us” launched a petition Wednesday calling on Democrats to withhold consent from Senate procedures. “The fate of our republic depends upon Senators refusing to conduct any further government business until there is an independent congressional investigation of President Trump’s abuse of power,” the petition states.

Part of the problem for Senate Democrats is that while they are furious over Trump’s decision to fire Comey, they also think it’s critical to get Republican buy-in for a more sweeping investigation. Asked if Democrats should withhold unanimous consent, Sen. Bob Casey (D-PA) noted that congressional Republicans would be needed for the formation of any bipartisan select committee.

“I think it’s got to be bipartisan — we have a lot of work to do,” Casey said. “So we haven’t made a decision on that.”