By Cokie Roberts and Steven V. Roberts

Pass the bill.

A bipartisan group of four senators has proposed legislation that would shield Special Counsel Robert Mueller should President Trump decide to order his dismissal. The measure could soon come up for a vote in the Judiciary Committee, and it merits strong support from both parties.

Yes, the bill is highly unlikely to become law. Majority Leader Mitch McConnell says he won’t even bring it to the Senate floor, and if it somehow passed Congress, Trump would certainly veto it. But a serious debate on Capitol Hill would sound a loud, clear warning to the White House: Don’t mess with Mueller.

As Sen. Susan Collins, a Maine Republican, said on ABC’s “This Week,” “having the discussion in Congress helps send a very strong message that we do not want Mr. Mueller’s investigation interfered with in any way.”

The president cannot fire Mueller directly. Ordinarily, he would order the attorney general to do that. But since the current A.G., Jeff Sessions, has recused himself from this case, the order would have to be executed by his deputy, Rod Rosenstein.

The bipartisan bill states that a special counsel can only be fired for “good cause.” The counsel would have 10 days to appeal a termination to a judicial panel. If the panel rules that the “good cause” standard has not been met, the counsel would be reinstated.

Mueller enjoys broad popular support. In the latest ABC/Washington Post poll, almost 7 out of 10 Americans back the special counsel’s investigation into possible collusion between the Trump campaign and Moscow. Large majorities also favor Mueller’s probes into the president’s business activities and payments by his lawyer to silence former girlfriends.

Two co-sponsors of the Mueller shield law, Republican Thom Tillis of North Carolina and Democrat Chris Coons of Delaware, stressed that public approval in explaining their proposal: “We have heard from constituents — Republicans, Democrats and independents alike — who agree that Special Counsel Robert Mueller should be able to conduct his investigation without interference. This should not be a partisan issue.”

No, it shouldn’t be. And that point was reinforced in a letter signed by hundreds of former Justice Department officials who have served presidents of both parties. “We served (the Justice Department) out of a commitment to the founding American principles that our democratic republic depends on the rule of law, that the law must be applied equally, and no one is above the law,” they wrote.

Republican leaders say the bill is not needed because Trump won’t sign it, and in any case, he would not be foolish enough to fire Mueller. “It’s not good politics in the end,” Sen. Orrin Hatch of Utah told Politico. “It says you don’t trust the president.”

That’s exactly what the bill says, because there’s no reason to trust the president. He clearly does not understand the “founding American principles” of an independent legal system, and he thinks his appointees should be loyal to him personally, not to the rule of law. Anybody who believes the White House line that Trump would never fire Mueller has learned nothing about this president’s capacity for impulsive vindictiveness and ego-driven outrage.

Trump has repeatedly denounced the special counsel’s investigation as “a total witch hunt,” and The New York Times reports that he’s already moved to remove Mueller twice — only to be dissuaded by more level-headed advisers. The list of aides he has fired in 15 months is staggering: from FBI Director James Comey and Secretary of State Rex Tillerson to his White House chief of staff and two national security advisers.

Moreover, many Trump loyalists are urging him to ax Mueller and denouncing Republicans like Tillis, who want to restrain the president’s worst impulses. But Tillis refuses to be bullied.

“Courage is when you know you’re going to do something that’s going to anger your base,” he told Politico. “The same people who would criticize me for filing this bill would be absolutely angry if I wasn’t pounding the table for this bill if we were dealing with Hillary Clinton. So spare me your righteous indignation.”

Like the former Justice Department lawyers, Tillis is standing up for the rule of law rather than the rule of one party or one president. His bill, he notes, could one day restrain a liberal Democrat — “a President Warren or a President Sanders or a President Booker” — just as it would restrain a Republican today.

His bill should pass. It would mark a rare moment of sanity in a capital that seems consumed by craziness.

Steve and Cokie Roberts can be contacted at stevecokie@gmail.com.