As we await the release of the Mueller report, an open question is whether evidence that the president’s actions rose to the level of obstruction of justice — the most likely impeachable offense in Mueller’s sights, according to most accounts of the investigation’s focus — will have any major impact on Donald Trump’s so-far impressive Republican support in fighting what he calls a “witch hunt.” The obvious precedent for believing that such a finding would erode his position even among Republicans is what happened to Richard M. Nixon in August of 1974, when the so-called “smoking gun” tapes were released (by order of the U.S. Supreme Court) showing him and his staff very clearly talking about suppressing any Watergate probe, well before the 1972 presidential election. As Politico noted on the 44th anniversary of this event, Nixon’s position deteriorated rapidly:

Nixon’s remaining political support on Capitol Hill all but disappeared. The 10 Republican members of the Judiciary Committee who had voted against impeachment in committee announced that they would now vote for impeachment once the matter reached the House floor.

Nixon lacked support in the Senate as well. Sens. Barry Goldwater (R-Ariz.) and Hugh Scott (R-Pa.), the minority leader, told Nixon that no more than 15 senators were willing to even consider an acquittal. Facing impeachment by the House and near-certain conviction in the Senate, Nixon announced his resignation on the evening of Aug. 8, 1974, effective as of noon on the following day.

Isn’t this sort of “ka-boom!” possible with respect to Trump? If it turns out Mueller’s got the goods on Trump having fired James Comey to obstruct justice, or told underlings to lie to Congress, or investigators to obstruct justice, or pursued any number of other scenarios a man like the 45th president might pursue to head off the hounds, you’d think there’d be some Republican heartburn, wouldn’t you?