Should the Massachusetts senator become president of the United States, she will undertake a historic bout of federal activism unmoored from any serious consideration of constitutional constraints.
This would far exceed the current "constitutional crisis" over the Ukraine controversy. Impeachment involves the House of Representatives exercising a responsibility clearly bestowed on it with broad latitude by the U.S. Constitution, to punish an act by President Donald Trump that was foolish and improper, but also squarely within his constitutional powers.
House Speaker Nancy Pelosi likes to say Trump violated the Constitution on his call with the Ukrainian president, but there’s no serious argument for this.