Titus 1:5
5I left you in Crete for this reason, that you would set in order the things that were lacking and appoint elders in every city, as I directed you—
Titus is left in Crete to put remaining things into order and to appoint elders in every city, as Paul directed. Wesley: ordain elders—appoint the most faithful, zealous men to watch over the rest; these were the elders, or bishops, that Paul approved of—men that had living faith, a pure conscience, a blameless life.
The church is not left without watchers. Living faith and a blameless life are the first credentials. Appointment is pastoral work, not a power-grab; Crete needs ordered towns, not a vacuum.
Calvin: churches cannot safely remain without the ministry of pastors. He does not give permission to Titus that he alone may do everything, but only bids him preside, as moderator, at the elections. This passage shows there is no distinction between a presbyter and a bishop.
Every town needs pastors. Titus moderates the appointing; he does not swallow the church. Elder and overseer name the same office. What remained is unfinished church order, not optional décor.