"There is no statute that criminalizes “abuse of power.” There is no common-law crime or misdemeanor that goes by that name. There is absolutely nothing. As a result, President Trump could not have violated established law merely by “abusing his power.” Also, impeachment is discussed throughout the Constitution, in the context of actual crimes that are tried to a jury by those who seek to convict the President. The Democrats themselves could not avoid the use of criminal language in their briefing: they asserted that the President must be “convicted” of abuse of power. But for whatever reason, they reject the idea that they must allege a crime.
Moreover, there are Constitutional constraints on the power of Congress that limit their ability to impeach a President for non-crimes. As Harvard Law Professor Nikolas Bowie explains, the Constitution contains prohibitions on so-called ex post facto laws (laws passed to make conduct criminal retroactively) and on bills of attainder (laws that are designed to target the conduct of one person). Given these constraints, it’s hard to understand why an impeachment power limited to “high crimes and misdemeanors” should be interpreted to allow the very abuse—arbitrary, individualized, and retroactive criminalization by a legislature—that the Founders had sought to prohibit."