Who were the Companions who pledged allegiance to the Messenger of Allah, peace and blessings be upon him, under the tree? What was the content of their pledge, and does this pledge resemble contemporary elections?

The Pledge of Allegiance (Bay'at al-Ridwan) was witnessed by 1400 or 1500 Companions, and they were the best people on Earth. The reason for the discrepancy in the number is due to rounding up or down, meaning they were more than 1400. Not all names of those who attended the pledge were collected, but some were mentioned, such as Abu Bakr, Umar, Ali, Jabir, Ibn Umar, and Umm Salama. The pledge was to fight to the death (jihad until martyrdom).