Can a President commit obstruction of justice?
Richard Nixon seemed to think so. (Well, he did eventually, although he first went full Trump with "When the president does it, that means that it is not illegal."). When Nixon was caught trying to get the CIA to obstruct an FBI investigation, he elected to resign rather than be kicked to the curb. His successor was worried enough about Nixon's potential criminal liability that he issued the Trickster one of those Presidential Get Out of Jail Free cards.
The articles of impeachment voted against Clinton also charged obstruction of justice, although impeachment is a civil action, not a criminal one, and it is extremely unlikely that he would ever have faced that charge in a criminal court.