Polygamy was practiced throughout the Old Testament-- not just when men died in wars. All of the patriarchs of the Jewish faith (Abraham, Isaac and Jacob) had multiple wives.
I think there are some very good arguments for polygamy-- if the man can support multiple wives, which is the only way it was allowed in traditional societies.
To wit, if wife one and two etc. can get along, isn't it better for them to combine households and not deprive one set of children of a father as would occur during a divorce? Also, you have built in baby-sitting which allows for cheaper childcare than you'd have in a divorce situation and allows women into the workforce with greater ease as a result.
It mitigates the two major problems that divorce causes children-- 1) economic decline because running two households is more expensive than running one and 2) lack of contact with Dad.
Between consenting adults, then, it's a way better option in terms of "family values" than divorce. BUt I doubt you'll see any conservatives making this case.
I know some people say it would cause immigration problems, but that could be solved by saying that -- as they do in the UK-- polygamy is fine but you can only bring one wife here from your country of origin.