President Donald J. Trump’s firing of FBI Director James Comey is unprecedented, as is much of what Trump has undertaken as president. Despite similarities with President Richard M. Nixon’s infamous “Saturday Night Massacre” 44 years ago, during the Watergate scandal, the political situations are utterly different.

In October 1973, Nixon, waiting until a weekend, ordered the dismissal of a newly appointed special prosecutor, Archibald Cox, who had issued a subpoena demanding that Nixon hand over secretly recorded – and, as would become clear, highly damning – White House tapes.

Nixon’s defiance was direct, and the result was disastrous. Attorney General Elliot Richardson and Deputy Attorney General William Ruckelshaus resigned in protest rather than carry out the president’s order. A federal judge ruled the firing of Cox illegal. Public opinion polls showed, for the first time, a plurality of Americans favoring Nixon’s impeachment.

It was the beginning of the end. Congressmen introduced impeachment resolutions. Nixon was forced to appoint a new special prosecutor. The drama thickened for another ten months, until the Supreme Court unanimously ordered Nixon to surrender the tapes. A few days after that, Nixon resigned rather than face certain impeachment and removal from office.

By contrast, unless the stars realign, Trump’s firing of Comey may mark the beginning of nothing, or at least of nothing bad for the president. Trump, like Nixon, may well be guilty of grave impeachable offenses – even graver offenses than Nixon’s. Trump, like Nixon, may have feared that unless he fired the person in charge of investigating him, some terrible revelation would be forthcoming. But, even if all this is so, Trump, unlike Nixon, may very well get away with it.

The two events differ in many ways, including their timing. By the time Nixon fired Cox, the Watergate affair had been building for far longer than the allegations about Trump and Russia have, so nerves had been rubbed raw.

The main differences, though, are political. In Nixon’s time, there were solid adversarial Democratic majorities in both houses of Congress, and there were also some Republicans, especially in the Senate, who put concerns about the Constitution ahead of concerns for their party. The Senate appointed a special select committee, headed by Democrat Sam Ervin and Republican Howard Baker, which heard testimony and gathered official evidence that led to the indictment of 40 administration officials and the conviction of several top White House aides, as well as to Nixon’s resignation.

Today’s Republican congressional majorities, however, have seemed singularly devoted to slowing and narrowing any serious inquiry into the thoroughly substantiated reports of Russian efforts to throw the 2016 election to Trump.