Coming off a landslide re-election victory in 1972, President Richard Nixon entered his second term with soaring approval ratings just shy of 70 percent. But by August 1973, Nixon would be even less popular than the current occupant of the Oval Office, with his approval ratings tumbling to an anemic 31 percent. What precipitated that nearly 40-point fall from grace was several months of congressional hearings in which the details of the Watergate burglary and Nixon's full involvement in it spilled out into public view.
The differences between Nixon’s situation and Donald Trump’s today are numerous. Trump hasn't won a single landslide election, and his approval ratings have never even topped 45 percent. Trump and his presidency have also been immersed in scandal since day 1, not to mention the fact that Trump isn't facing just one distinct investigation but rather multiple probes into numerous areas of both his private and professional life.
In that sense, one day of public testimony from Trump's former fixer/lawyer Michael Cohen can't possibly train the kind of granular focus that several months of testimony from multiple insiders did on Nixon and Watergate. Nonetheless, after he spent a decade doing some of Trump's dirtiest deeds, Cohen's testimony could absolutely reveal a dagger that ultimately deals a deadly blow to Trump’s presidency.
In anticipation of Wednesday’s hearing, many people have suggested Cohen's testimony will be his "John Dean moment," invoking Nixon's former White House counsel, who famously testified that he had warned the president there was "a cancer growing on the presidency." But Nixon's ultimate undoing really came from Alexander Butterfield, a deputy assistant to the president, who revealed that a recording systemhad been installed at the White House. When Butterfield was asked on July 16, 1973, if he was "aware" of such a system, he finally responded, at the tail end of a pregnant pause, "I was aware of listening devices, yes, sir."

