Zhang Jun/Zumapress

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.

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…