That includes abuse of office in the form of serious accusations against political opponents if they turn out to be false and made without evidence. These, too, deform the democratic process.

The Constitution speaks of impeachment for "high crimes and misdemeanors." A lot of ink has been spilled over these words, which date back at least to impeachment proceedings in the 14th century. This isn't the place for a detailed analysis.

Suffice it to say that what makes crimes "high" is that they pertain to the exercise of government office. That's exactly what accusations by the executive are: actions that take on their distinctive meaning because they are made by government officials.

What's more, government acts that distort and undercut the democratic process are especially serious and worthy of impeachment. The Watergate break-in to the Democratic National Committee headquarters was part of an effort to steal the 1972 election. A wiretap of Trump's campaign would've had political implications.

And accusing the past Democratic president of an impeachable offense is every bit as harmful to democracy, assuming it isn't true. Obama is the best-known and most popular Democrat in the country. The effect of attacking him isn't just to weaken him personally, but to weaken the political opposition to Trump's administration.