Politics and politicking in Nigeria has assumed a considerably new dimension. Actors articulate their ideology and programmes, and construct their subjects and experiences in diverse linguistic processes with a view to achieving political victory. This paper examines clause structures of President Buhari's "My Covenant with Nigerians" to reveal the transitivity processes employed by the President in this famous campaign speech in 2015 presidential election. This study utilized "Transitivity Processes," which is rooted in Halliday's (1985) "Systemic Functional Grammar," in order to uncover different process types and main participants in the speech, and to explain the functions which these processes perform in the speech in helping the speaker to convey his ideology to Nigerians and convince them to rally support for him. Specifically, objective of this study is the uncover transitivity process types in the speech, their frequency, function and ideological underpinnings. The study reveals that President Muhammadu Buhari utilized mental and verbal processes perception, affection, cognition and volition, and verbal process of "saying" to appeal to the masses, and to commit himself to serve Nigerians. He equally used material and relational processes to encode his ideology, persuade the people and achieve political victory.