Peace Pagluu
By the way we don't believe Abu Bakr (RA) was successor ... there is no successor to Muhammad (SAW) he is and will be the Prophet of our time until the end of days.
Abu Bakr (RA) was the first Khalifa. (translation ... caretaker) appointed by the people who were of highest calibre from the Ahl-al-Bayt.
Peace upon you too brother,
Khalifa actually do mean 'successor'. The actual term is "Khalifatur Rasool Allah", i.e. successor of the Prophet of Allah.
Which people of the 'high calibre' appointed Abu Bakr exactly?