First a quick question. Who was the last U.S. President to be impeached? Think. Got it? For bonus points you can guess what he was impeached for. I was surprised when I was researching this last night, the answer is Bill Clinton for perjury and obstruction of justice. The only other president to be impeached was President Andrew Johnson in 1868 and he was also the first. Last night I was wondering if it were actually possible for a U.S. President to be successfully impeached and convicted. While in theory it can happen, in practice I don't think we'll ever see it.
Johnson proved that is was possible to get this conviction against such a high ranking official. But it took President Nixon to teach his successors how to beat this charge. President Nixon was almost certainly going to impeached by the House and convicted by the Senate so (probably) struck a "corrupt bargain" with his Vice President Gerald Ford. "I give you the Presidency and you give me a blanket pardon." which is exactly what happened. Is this a cynical view or a realist one?
Provided that it's in the best interests of the Vice President to accept a promotion and (probable) re-election and the President's best interests to not get convicted this deal would be easily struck. It's in their political parties best interest as they retain control of the executive branch. It's in the countries best interest to not get a President convicted of a crime. Thus, it follows that a U.S. President can do whatever he wants and will never get convicted of anything.