All the “Biden campaign sources” saying it.
Several anonymous sources said that they thought that he would not run again. Why do you believe anonymous sources opinions?
Is Biden not a "Biden campaign source"? Because he explicitly said he had no intention of running only one term.
And why have you abandoned your original claim of a Biden promise?
Yes, words have meaning. Biden said “I don’t have any plans on one term.” Why does some vague suggestion of being a 'bridge' get you to ignore those very easy to understand words?