Can a federal official be impeached and convicted after he has resigned or otherwise left office? (For example, could the impeachment of President Nixon have proceeded after his resignation? Or could Hillary Clinton be impeached now for crimes committed while she was Secretary of State?)
If the answer is no, then at what point in the process can an impeachment be thwarted by resigning? It seems unreasonable that the culprit should be able to escape the harsher penalty of disqualification from holding office in the future, by resigning just before the result of the vote to convict is announced in the Senate.
