It is the true and wondrous right dharma that is the One Vehicle. It is the unexcelled practice that perfectly embodies all good acts. Single-heartedly practicing the nembutsu is a single voicing. A single voicing is saying the Name. Saying the Name is constant mindfulness.
Constant mindfulness is right-mindedness.
Further, naishi ichinen in no way refers to one thought in contemplation on the Buddha's virtue or to one utterance in repeated recitation of the Name. Let this be known. Pure shinjin is shinjin that actualizes Amida's profound and vast benefiting of others. This is because we do not depend on Amida's directing of virtue for our going forth and because we are entangled in a net of doubt. It is through the Tathagata's supportive power, and through the vast power of great compassion and all-embracing wisdom, that a person realizes pure, true, and real shinjin.