From New York Magazine:

The same would be true of the larger investigation, which has a criminal component now playing out in the courts, as well as a counterintelligence one that remains, in great part, a closely guarded secret. NBC News’ Pete Williams, who has covered federal law enforcement for the better part of the last 25 years, ran through several of the hypotheticals surrounding a Mueller firing and concluded that, in the end, Trump would pay a steep political price but the show would go on. “The probe would simply revert to the FBI and the Justice Department, where prosecutors and federal agents would continue the kind of work they were doing before the special counsel was appointed,” Williams wrote, matter-of-factly. Paul Rosenzweig, a former senior counsel in Kenneth Starr’s investigation into Bill Clinton, more or less landed in the same place. “It would come at severe political cost to the president and, quite likely, have relatively little actual effect on the current investigation,” he wrote for The Atlantic.