Simplify the following text for a Grade 14 native English-speaking person.
Original: Gerald Ford was the first Vice President selected by this method , after the resignation of Vice President Spiro Agnew in 1973 ; after succeeding to the Presidency , Ford nominated Nelson Rockefeller as Vice President .
Simplified: This has happened twice , first after Gerald Ford became Vice President after the resignation of Spiro Agnew , and second after Nelson Rockefeller became Vice President after Gerald Ford became President when Richard Nixon resigned .