The vice president becomes the president if the president dies. Such is the main reason for the office of vice president.
John Tyler
Yes
He was the first president who got into office not by vote, but by the president dying (William Henry Harrison).
Theodore Roosevelt
John Tyler is the first United States President to take office following the death of an elected President. He replaced William Henry Harrison, who died on April 4, 1841
Harry S Truman, who was vice president, became president.
Following the death in office of President William Henry Harrison, there was a vacancy in the office of Vice-President until March 4, 1845.
Hoover was at the start, and then FDR became President and was President until his death.
Andrew Johnson
no
When a President dies in office, the Vice President automatically replaces him. There is no election until he finishes the deceast President's term of office. So, I'm not sure if that is what you intended to ask.