Terrorism or abuse of power or crime
Nobody. A president continues to serve in office when he is impeached. If he is convicted and removed from office, the vice-president becomes president, same as if the president were to die.
The constitution states the terms of office and how a president or Vice President can be removed from office.
the vice president
No. If the President runs for a second term of office, he may name a different person as running mate provided the nomination convention approves, but he can not fire an elected vice president. A Vice-President can only be removed from office involuntarily by impeachment in the House of Representatives and conviction by the US Senate.
Vice President takes over
If a president is impeached by the House of Representatives, the Senate has the responsibility of conducting a trial to determine whether the president should be removed from office. The Senate acts as the jury in this trial, and two-thirds majority vote is required to convict and remove the president. If convicted, the president would be removed from office and the vice president would assume the presidency.
If the President of the United States is removed from office, the Vice President immediately becomes the new President. Then, the Speaker of the House of Representatives becomes the President if the Vice President is unable to assume the role. The President Pro Tempore of the Senate would be next in line if both the Vice President and the Speaker of the House are unable to take on the presidency.
If both the President and Vice-President are removed from office, the job passes to the Speaker of the House of Representatives, followed by the President pro tempore, Secretary of State, Secretary of the Treasury, Secretary of Defense, and the Attorney General.
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. Being impeached is roughly equivalent to when a criminal is indicted or charged with a crime. After that a trial is held and unless they are convicted, nothing happens. Both Andrew Johnson and William Jefferson Clinton were impeached. Neither was convicted by the Senate so they each remained president. If the Vice President is impeached as well, the Speaker of the House becomes President.
No, if the President is removed, retires or dies the Vice President will become President. If the Vice President can't fill the office for some reason then next in line is the Speaker of the House of Representatives.
Clinton remained president through the end of his term. Had he been removed from office, it would have gone to Vice President Al Gore.
No, however Nixon's VP, Spiro T Agnew did resign shortly before Nixon did. He was indicted for crimes he committed before he was vice-president. Part of his plea bargain deal was that he would resign as VP, so in a way, he was removed from office.