The so called Two Kingdom view of the separate institutes of secular state vs the church identifies a fairly clear boundary between the authority of each: one demanding some compliance with a nominal set of ethical behaviors for the well being of both Christian and all members of society of any religious persuasion and includes powers (e.g. punishing injustice, warfare) while the other holds higher standards in both ethical and spiritual matters but who's authority is limited in scope to the spiritual (e.g. sacraments, doctrine).
According to adherents of this view1, ordained church office bearers carry a special authority over spiritual matters in the context of the church. Likewise those who hold public office under any political structure2 have a special charge to create and enforce laws that fulfill a specific purpose. Given the the separation between both domain and available powers, under any circumstances would it be valid for an individual man to hold both ordained office in the church and a public office3 in the state? Is such a dual role4 possible for an office-bearer in the same way that it would be for a normal Christian to maintain any political role or is there a fundamental conflict of interest in being ordained resulting in some sort of unacceptable schizophrenia?
If there is a difference between the thinking of Reformation era theologians who used "two kingdom" terminology (viz. Martin Luther, John Calvin) and the modern "Radical Two Kingdoms" theological framework (viz. Meredith Kline, Michael Horton) on this issue, I would like to hear the difference between them spelled out.
1 Please note that this is not the quite same as the modern Evangelical parlance of "separation of church and state". Please limit answers to actual implementations of Two Kingdom theology.
2 For the purposes of this question the sort of public office I am referring to might be characterized by those of a mayor or constable—offices that are charged with either legislating or enforcing civil structures as their primary responsibility.
3 I am not thinking of the sort of office that might be conferred by the state automatically to religious office holders such as the right to officiate marriages, I'm thinking more along the lines of mayor or constable or parliamentary representative.
4 I am aware that most 2K views see all Christians as holding dual citizenship. This question is not about citizenship or the roles of all believers but specifically about office bearing.