(CNN) There is a truly remarkable number in the most recent CNN poll, conducted by SSRS and out this morning.

In it, 42% of Americans say President Donald Trump should be impeached and removed from office.

What makes it remarkable is that he's on par with President Richard Nixon, who 43% of Americans said should be impeached and removed from office in a March 1974 Harris poll. That was after the scale of Watergate came to light, but months before the House started to move against Nixon, who would go on to resign in August 1974 rather than be impeached.

Impeachment requires "treason, bribery or other high crimes and misdemeanors," according to the Constitution, which also lists it as the the only thing for which a President can't issue a pardon.

Trump has bragged that he certainly has the power to pardon himself but won't need to use it. Nixon got a pardon from Gerald Ford, the man to whom he gave the keys to the White House.

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