Since the proposed impeachment of the President is by collusion with a foreign power, the opponent to the President during the previous election would become the President, unless that person is also convicted of crimes of the people. read more
The 25th Amendment, Section 1, clarifies Article II, Section 1, Clause 6, stating unequivocally that the vice president is the direct successor of the president, and becomes president if the incumbent dies, resigns or is removed from office. read more
The vice president becomes the new President if the President vacates his office for any reason, including death, resignation, or forced removal via the impeachment process. Note that the President would remain president after impeachment until and unless the Senate votes to convict. read more