Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Synods of Sardica, Carthage, Constantinople, and Carthage Under St. Cyprian, Which Canons Were Received by the Council in Trullo and Ratified by II. Nice.: Canon LXXIV

Canon LXXIV.  (Greek lxxvii.)

That no bishop who is an intercessor is to hold the see where he is intercessor.

Item, it has been decreed that it is not lawful to any intercessor to retain the see to which he has been appointed as intercessor, by any popular movements and seditions; but let him take care that within a year he provide them with a bishop:  but if he shall neglect to do so, when the year is done, another intercessor shall be appointed.

Notes.

Ancient Epitome of Canon LXXIV.

It seemed good that the bishop who had been called in as an intercessor, by the zeal and dissensions of the people, should not be allowed to become the occupant of its throne:  but let a bishop be provided within a year, or else in the next year let another intercessor be appointed.

This is Canon IX. of Carthage, September, a.d. 401.

Johnson.

We here call this officer “Guardian of the spiritualities” in the vacancy of the see.