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On Thursday, four Republicans joined their Democratic colleagues on the Senate Judiciary Committee to take a major step towards formally protecting Mueller from an ouster by the president: They voted to approve legislation that would take the power to fire Robert Mueller, the special counsel running the Trump-Russia investigation, out of the president’s hands, and create a process to review a special counsel’s firing, and possibly reinstate them.

Thursday became the first time lawmakers voted to protect Mueller.

For weeks now, President Donald Trump’s aides have dropped hints that the president is considering firing Mueller, and that Trump believes he has the authority to do so. The Special Counsel Independence and Integrity Act was proposed earlier this month, and would clarify that only a senior Justice Department official would have the authority to fire the special counsel, and only after providing written cause. The bill also requires an expedited court review of the special counsel’s termination. Should the court find that the firing was not for good cause, the special counsel must return to their job.

This bill combines two older pieces of bipartisan legislation proposed by the sponsors this past August. Neither of those proposed bills made it out of committee, making Thursday the first time lawmakers have voted to protect Mueller. The committee’s vote came the same morning that Trump, in an interview on Fox and Friends, warned that he would soon get “involved” in the work of his Justice Department—a cryptic statement that could signal Trump will try to interfere with the special counsel.

The bill will now move to the full Senate for consideration. Senate Majority Leader Mitch McConnell has said he’s opposed to bringing the bill to the Senate floor, where it is unlikely to gain the 60 votes needed to move on to the House.