The other element was that the congregation had a role in ratifying the election/ordination of priests and deacons by announcing "Axios!" (He is worthy), which is still part of the ordination rite in Eastern Orthodox churches, a relic from the time when clergy were drawn from the congregation.  Today, an ordination to the priesthood or diaconate would not be invalid if the congregation withholds the "Axios", but you can bet that the clergy would problems being accepted by a parish without it.