Does Congress know something we don't about whether President Trump is again considering firing special counsel Robert S. Mueller III? (Or fire the aides who refuse to fire Mueller for him?)

That's a fair question to ask after a flurry of movement Tuesday from senators on both sides of the aisle who reaffirmed their commitment to letting Mueller finish his investigation into Russia interference in the 2016 election and whether the Russians coordinated with the Trump campaign.

“We urge President Trump to allow the Special Counsel to complete his work without impediment,” Sens. Thom Tillis (R-N.C.) and Christopher A. Coons (D-Del.), authors of a bill to protect Mueller, said in a joint statement seemingly out of the blue, “which is in the best interest of the American people, the President, and our nation.”

Tillis and Coons introduced a bill nearly a year ago that would allow Mueller to challenge his firing in court if he ever needed to. That and another bipartisan bill to protect Mueller have never gotten past a September hearing, even as Trump's attacks on Mueller have escalated.

Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa), the gatekeeper for such bills, has said he's worried that it could be unconstitutional to limit which members of the executive branch the president could fire or hire.

(Side note: Trump technically can't fire Mueller, who answers to Deputy Attorney General Rod J. Rosenstein. But Trump could fire Justice officials who refuse to fire Mueller until he finds someone willing to do it. Alternatively, Trump could fire Mueller himself and risk major legal challenges.)

Tillis's and Coons's offices said there was no particular reason or event that prompted their statement Tuesday, other than the senators wanting to reiterate their support for the special counsel. And, presumably, to remind the rest of Congress that their bill still exists.

But the fact that Tillis, a Republican, felt he had to say anything right now raised eyebrows in Washington. Especially since Republicans didn't seem particularly eager to take up the legislation after Trump directly attacked Mueller for the first time earlier this month.

Adding to the intrigue of what Congress may know, a number of Senate Democrats issued their own statement Tuesday indicating they were worried that Trump could fire Mueller while Congress is out of town on a two-week break. Sen. Richard Blumenthal (D-Conn.) and eight other Democrats on the Senate Judiciary Committee sent a letter to five Justice Department officials asking for their commitment to protect Mueller.

I'm excerpting a sizable chunk of the letter, with the highlights in bold:

[W]e have significant concerns that the president or his White House could order individuals at the Department of Justice with the authority to oversee Special Counsel Mueller’s probe to interfere with the probe or shut it down. You fall in the line of succession at the Department of Justice if Deputy Attorney General Rosenstein were to either resign or be removed. We write to request that you provide a written and public commitment that you will not interfere in the Special Counsel’s investigation into Russian meddling in the 2016 elections, possible collusion with such meddling by the Trump campaign, efforts to obstruct justice, and any related inquiry.

In an interview Tuesday night with MSNBC's Rachel Maddow, Blumenthal cited “swirling,” “unconfirmed” reports that raised his alarm that the president may be attempting to fire Mueller. “With Congress now out of town and therefore unable to take action, this is meant to send a warning,” Blumenthal said of the letter.

Blumenthal didn't share anything in that interview that hasn't already been reported. The New York Times and Washington Post reported in January that Trump tried to fire Mueller in June. The Times also recently reported Trump then may have moved to publicly deny he ever thought about firing Mueller. And after Attorney General Jeff Sessions fired top FBI official Andrew McCabe hours before McCabe was set to retire earlier this month, Trump started attacking Mueller directly by name.

It's not lost on lawmakers and observers that Trump is debating whether to sit down with Mueller for a potentially perilous interview, with a quickly thinning legal team in disarray. Meanwhile, Mueller's investigation inches closer to the president, with news Wednesday that a former Trump aide who is likely cooperating with Mueller had regular contact with someone who had ties to Russian intelligence and news that Trump's former lawyer broached the subject of pardoning two of Trump's former campaign aides.

The last time Congress left Washington for an extended period, none of that had even happened or been reported. And Democrats publicly warned Trump not to fire Mueller then, too. Sen. Mark R. Warner (D-Va.), the top Democrat on the Senate Intelligence Committee, went on the Senate floor before Congress's December break and warned Trump that firing Mueller would be a “gross abuse of power.”

So clearly there's a pattern here of Congress leaving town, and some lawmakers getting skittish that their absence will embolden Trump to do something we know he's already considered at least once.

The Times has reported that Trump's aides were never quite sure the president fully backed away from firing Mueller.

It sounds as if some members of Congress aren't, either.

Aaron Blake contributed to this report.