WASHINGTON — Yesterday, we posed this question: Would congressional Republicans draw a line in the sand when it comes to protecting special counsel Robert Mueller? The answer we got 24 hours later: While they haven’t raced to pass legislation, several GOP senators did fire warning shots at President Trump, NBC’s Rebecca Shabad writes.

“Sen. Chuck Grassley, R-Iowa, chairman of the Senate Judiciary Committee, said on the Fox Business Network on Tuesday that he had ‘confidence’ in the special counsel and that ‘it would be suicide for the president to fire Mueller.’”

“Sen. John Kennedy, R-La., said he thought Trump was ‘too smart’ to get rid of Mueller. ‘I think it would provoke some sort of reaction by Congress. I think he knows that,’ Kennedy said on CNN's ‘New Day,’ adding that ‘the president can't just fire Mr. Mueller. He's got to direct Mr. Rosenstein to fire him, and I don't think Mr. Rosenstein would do it.’”

“Sen. Bob Corker, R-Tenn., said it would be ‘inappropriate’ for Trump to dismiss either Mueller or Rosenstein. ‘I think it would be a massive mistake for the president to do anything to interfere with this investigation,’ said Corker, adding, ‘he knows most every Republican senator feels that way.’”

“And Sen. Lindsey Graham, R-S.C., also said Tuesday that he didn't think Trump was likely to dismiss either man because he knew ‘it would be the beginning of the end of his presidency.’”

What’s more, NBC’s Garrett Haake notes that a bipartisan group of senators — Graham, Thom Tillis, R-N.C., Chris Coons, D-Del., and Cory Booker, D-N.J. — are today introducing a bill that would codify that a special counsel could be fired only for good cause by a senior Justice Department official and would preserve all of the investigation’s documents and staff while the case is pending.

So these are definite cracks in the ground between Trump and his party, at least in the Senate. And they come at a time when congressional Republicans are upset at Trump on other matters like the tariffs, as Axios reports.

It’s now DEFCON 2 at the White House when it comes to Mueller

When yesterday began, we wrote that the situation at the White House was at DEFCON 3 (increased readiness) after the news of Monday’s FBI raid of Trump lawyer Michael Cohen and after Trump’s “A TOTAL WITCH HUNT” tweet.

And this morning, you could make a good case that the situation is now at DEFCON 2 (Cuban Missile Crisis level) after reports that Trump is considering firing Deputy Attorney General Rod Rosenstein, of a “meltdown” at the White House and about the president losing his sh!%.” (DEFCON 1 is imminent nuclear war.)

CNN: "President Donald Trump is considering firing Deputy Attorney General Rod Rosenstein, multiple people familiar with the discussions tell CNN, a move that has gained urgency following the raid of the office of the President's personal lawyer."

The New York Times writes that Trump sought to fire Mueller in December: "In early December, President Trump, furious over news reports about a new round of subpoenas from the office of the special counsel, Robert S. Mueller III, told advisers in no uncertain terms that Mr. Mueller’s investigation had to be shut down... In the hours that followed Mr. Trump’s initial anger over the Deutsche Bank reports, his lawyers and advisers worked quickly to learn about the subpoenas, and ultimately were told by Mr. Mueller’s office that the reports were not accurate, leading the president to back down."

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Also in the Times: “Inside the White House, Mr. Trump — furious after the F.B.I. raided his longtime personal lawyer, Michael D. Cohen — spent much of the day brooding and fearful and near what two people close to the West Wing described as a ‘meltdown.’”

Politico: “A GOP operative close to the White House told POLITICO: ‘The all-caps tweet, that’s the primal scream. That’s the war cry.’ ‘He’s losing his sh!%,’ the operative added. ‘We’re at a different level now.’”

Axios: “Sources close to the president genuinely fear special counsel Robert Mueller has passed a ‘breaking point’ for Trump. More than one person has used that phrase to us. They worry the president will fire Mueller”.

And folks, we haven’t even gotten to the upcoming Comey interview yet. Or the breaking news via Axios — at our publication time — that House Speaker Paul Ryan won’t run for re-election.

If Trump is trying to project calm, he’s not tweeting that way

In the span of four tweets this morning, Trump goes from saying things are “very calm and calculated” at the White House — to warning Russia that missiles are coming in Syria, and that the United States’ relationship with Russia is now worse than it was during the Cold War. (Really?)

Tweet #1: “So much Fake News about what is going on in the White House. Very calm and calculated with a big focus on open and fair trade with China, the coming North Korea meeting and, of course, the vicious gas attack in Syria. Feels great to have Bolton & Larry K on board. I (we) are”

Tweet #2: “....doing things that nobody thought possible, despite the never ending and corrupt Russia Investigation, which takes tremendous time and focus. No Collusion or Obstruction (other than I fight back), so now they do the Unthinkable, and RAID a lawyers office for information! BAD!”

Tweet #3: “Russia vows to shoot down any and all missiles fired at Syria. Get ready Russia, because they will be coming, nice and new and “smart!” You shouldn’t be partners with a Gas Killing Animal who kills his people and enjoys it!”

Tweet #4: “Our relationship with Russia is worse now than it has ever been, and that includes the Cold War. There is no reason for this. Russia needs us to help with their economy, something that would be very easy to do, and we need all nations to work together. Stop the arms race?”

Highlights of Mark Zuckerberg’s Tuesday on Capitol Hill

Here’s NBC’s wrap on yesterday’s Senate hearing featuring Facebook’s Mark Zuckerberg:

Someone at Facebook has a lot of homework to do: “When Zuckerberg didn't have a specific answer to a question, he punted to a familiar response: ‘I'll have someone on my team get back to you.’ Whether that follow-up between the committee and Facebook actually happens will remain to be seen. However, it's safe to say that someone at Facebook may have a lot of homework coming their way.”

Is Facebook a monopoly? “When Zuckerberg began naming different categories of competitors who may overlap with what Facebook is doing, [Sen. Lindsey] Graham stopped him to ask if there was any direct, comparable alternative to Facebook. He then flat-out asked Zuckerberg whether Facebook was a monopoly. ‘It certainly doesn't feel like that to me,’ Zuckerberg said.”

Zuckerberg agrees Facebook is ‘responsible for the content’: “In his strongest statement yet on the topic, Zuckerberg acknowledged that Facebook is responsible for the content on its platform. Facebook and other platforms have for years used ‘safe harbor’ as a reason to absolve themselves of responsibility for what is on their platforms. This admission could potentially spell changes for Facebook and other major tech companies if safe harbor is no longer accepted as the norm.”

Zuckerberg today testifies before the House.

Rundown on the 2018 midterms

In case you missed them, here are some of the recent midterm developments that we’ve chronicled on our “Rundown” blog: A Harvard Institute of Politics poll shows that 37 percent of those ages 18-29 say they will definitely vote in the 2018 midterms – up from 23 percent who said this in 2014… NBC’s Shaquille Brewster writes about Richard Cordray’s TV ad invoking Obama in Ohio’s gubernatorial race… And South Carolina’s attorney general won’t bring charges against Rep. Ralph Norman, R-S.C, who brought a loaded gun to a campaign event.

Meet the Press presents “The Lid”

And be sure to check out our afternoon/evening flash news briefing — The Lid. Whether it’s news about politics, election data, our industry-leading polls, Chuck Todd and the NBC News Political Unit run down the most important stories from Washington every weekday evening to help you make sense of it all.