Rabiu Kwankwaso, senator representing Kano central, led some of his colleagues to the presidential villa in Abuja on Monday.
Kwankwaso is among the lawmakers believed to be planning their exit from the ruling party.
His rift with Abdullahi Ganduje, governor of the state, made him stay away from the convention of the APC.
He rather chose to visit Atiku Abubakar, a Peoples Democratic Party (PDP) presidential aspirant on the day of the convention, and he has been listed as one of the lawmakers in the R-APC, though he is yet to acknowledge this publicly.
Kwankwaso contested the presidential ticket of the APC in 2014, and came next to Buhari followed by Atiku.
The presidency has been making last-minute effort to prevent key members of the APC from leaving the party.
On Monday night, Kwankwaso and some of his colleagues were sighted at the presidential villa alongside Abubakar Badaru, Jigawa state governor.
Buhari met with Senate President Bukola Saraki last week.