Q: Is the deacon able to co- lead the Penitential Rite at the commencement of a Mass. I presume the priest or bishop offers the absolution.
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A: A deacon may lead the third form of the penitential act at Mass, the one that includes three invocations addressed to Christ. In fact, anyone may lead it: the cantor, the reader, or some other person in the congregation.
The priest is supposed to lead the second form at Mass because it is a reduced version of the former prayers at the foot of the altar. The first form, the confiteor, may be started by anyone. You are correct that the priest or bishop presiding says the absolution in all forms.