For those studying for the Twitter Bar Exam, here are the standards:
Preponderance of evidence (51% or better)
Clear and convincing
Beyond a reasonable doubt (highest level, for criminal trials)
I'd argue that it should be easier to remove a corrupt president than to put a person into the electric chair.
I'd concede that that is the correct standard. More than a mere preponderance, but not requiring the level of certainty for criminal matters.