As the APC primary election approaches, President Muhammadu Buhari is said to be considering announcing his preferred successor to provide the delegates guidance in the party primary poll.
However, given the current situation, these two politicians stand the best possibility of becoming President Buhari’s favorite men, as he is heavily invested in the person who would succeed him.
Prof. Yemi Osinbajo:

Vice President Yemi Osinbajo, who is now working with Buhari, appears to have a good possibility of becoming President Buhari’s preferred choice.
Remember that Buhari said a few weeks ago that the ACN caucus, of which Osinbajo is a member, will elect the party’s flag bearer in 2023.
Although Osinbajo is not the only ACN caucus member wanting the presidency, the fact that he is now a member of the presidential team, his age, and his good health may persuade Buhari to choose him.
Good luck Jonathan:

Currently, Jonathan has not stated his intention to run for president, but he is said to be evaluating the idea in the hopes of jumping into the race shortly. Jonathan and President Buhari appear to have been closer in the previous five months, as they have conducted numerous meetings together, and there are some APC cabals trying everything they can to get Jonathan to join the APC and let him run for the presidential primary.
President Muhammadu Buhari may adopt the same approach he employed when he chose Abdullahi Adamu, who had no intention of becoming the APC national chairman.