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Republicans are insulating Trump in case he fires Robert Mueller.

Before this week, the investigation into Russian interference in the 2016 election faced two major crises. The first occurred when President Trump fired FBI Director James Comey; the second occurred over the summer, when Trump was clearly agitating to either pardon himself or fire special counsel Robert Mueller, who had been appointed in the wake of Comey’s removal. In these instances, Trump was either trumped or held in check. Republicans made it clear that firing Mueller would be a huge mistake, although they did not pass any legislation to protect the special counsel’s investigation.

Now, the investigation is once again in crisis. The New York Times reported that Trump had ordered Mueller to be fired in June, only to beg off after White House counsel Don McGahn threatened to resign in protest. It is widely suspected that this was leaked because Trump is once again considering firing the special counsel. Meanwhile, Andrew McCabe appears to have been pushed out of his position as deputy director of the FBI, raising questions about the independence of the agency’s director, Christopher Wray. And House Republicans have made public a highly misleading memo that alleges that the Mueller investigation and the FBI are dominated by agents who are out to get the president.

This last development is crucial to understand what makes this crisis different from the ones that preceded it. In the past, Republicans had largely drawn a line in the sand to protect the integrity of law enforcement. Now, with the release of the memo, they are actively participating in the president’s campaign to discredit the special counsel. The memo insulates Trump, no matter what happens next. It buttresses the case for firing Mueller. It also gives Trump ammunition to discredit the special counsel, should Mueller find that the president obstructed justice. In any case, it signals that if Mueller does find wrongdoing that Congress will do nothing—in fact, Republicans will join the president in saying the investigation was corrupted.