If that were to happen, impeachment and we get Biden, who is up for the VP slot in that event? Reid?
Actually, it is Speaker of the House [Boehner]
Then:
President Pro Tem of the Senate [longest serving Senator, Inouye from Hawaii]
After That:
Cabinet Secretaries [in order of establishment of office, first one being Secretary of State, then Treasury, Defense, Attorney General, Interior, Agriculture, Commerce, Labor, HHS, HUD, Transportation Energy, Education, Veteran's Affairs, and Homeland Security]
Then, it goes back to the Senate and the House - don't know in what order ...