What are “high crimes and misdemeanors,” the constitutional grounds for impeachment? According to President Trump’s lawyers, they must be, at the very least, actions that could be charged as serious crimes.

The central charge by House Democrats — that Trump abused his powers by withholding military aid to coerce Ukraine into investigating a potential Democratic opponent, Joe Biden — “alleges no crimes at all, let alone ‘high crimes and misdemeanors,’ as required by the Constitution,” the president’s legal team stated in its initial filing to the Senate.

…

Advocates of a broad view of impeachment also make historical arguments. Robert Weisberg, a criminal law professor at Stanford, said extortion and bribery, crimes “very much in the nature” of Trump’s alleged dealings with Ukraine’s president, were not defined as federal crimes until well into the 19th century, but were clearly impeachable much earlier.