Someone in the know told me it's looking more like

[kst]

106. Impeachment vs. criminal prosecution

There isn't really any precedent for arresting a sitting President for a crime.

Two Presidents (Andrew Johnson and Bill Clinton) have been impeached and acquitted, and one more (Nixon) resigned in the face of inevitable impeachment.

i think the expectation is that if, hypothetically, a President were guilty of a crime, he would be impeached, convicted, and removed from office and then criminally prosecuted. I don't see anything in the Constitution protecting the President from arrest (if someone can correct me on that please do), but a President under arrest is still the President, which would be ... awkward.

US Constitition, Article II, Section 4:

The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.

And Article I, Section 3, Paragraph 7:

Judgment in Cases of impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States: but the Party convicted shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law.

(Note that treason and bribery are the only two crimes specifically called out as grounds for impeachment.)