Drury comments on 1 Tim 3, says the passage does not appear to prohibit polygamy.
Clare Drury, "The Pastoral Epistles," in The Oxford Bible Commentary, ed. John Barton and John Muddiman (New York: Oxford University Press, 2004), 1224–25
The list of virtues expected of such a community leader is conventional in both Jewish and Hellenistic societies, including that favourite 'restraint' (sophrosune, translated in the NRSV as 'temperate'). His duties include a responsibility for teaching, that is handing on the tradition as he has had it handed on to him. There are some points that may be surprising to a modern reader; the episkopos is expected to be married and to be the head of a household (3:2,4-5). Furthermore he is to be 'married only once', literally, 'the husband of one wife'. Polygamy is not being forbidden here; remarriage after divorce may be in question, or it may be that the remarriage of widowers is also excluded for episkopoi. If so, the rules are different for different groups in the community, for young widows are encouraged to remarry (5:14). Perhaps, though, this is rather an extreme translation of the Greek; what is meant is that the episkopos should be a faithful husband to his wife, but that sequential monogamy is not out of the question. His conversion to Christianity must not be recent. There may have been important individuals in the community who felt that their standing or wealth qualified them to become leaders in the church. But to be an episkopos one must be firmly rooted in the faith; the implication must be that the church itself is firmly established too.