According to Two Kingdom theology, could a man hold both secular and spiritual office? 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.
This is an interesting question.  Bear with me as I attempt to build a bit of Confessional background to my answer.  

It's clear from Article 5 of the Augsburg Confession that the office of the ministry was instituted by God to preach the Gospel and administer the Sacraments (http://bookofconcord.org/augsburgconfession.php#article5).  This is God's "Right Hand Kingdom or Realm."  See also articles 7 and 8 in the Confession.  Then, the Confession notes that no one should do these things "publicly" (i.e. in the name of a congregation) unless he be regularly (or rightly) called (Article 14).

Then, Article 16 talks about Civil Affairs (http://bookofconcord.org/augsburgconfession.php#article16).  This is God's "Left Hand Kingdom or Realm" of civil government.  It's interesting that in this Article there is no distinction between the various offices; i.e. "it is right for Christians to bear civil office, to sit as judges, to judge matters by the Imperial and other existing laws, to award just punishments, to engage in just wars, to serve as soldiers, to make legal contracts, to hold property, to make oath when required by the magistrates, to marry a wife, to be given in marriage."  In this Article, bearing a civil office is lumped in with marrying a wife.  Then, you have Article 23 later which states it is right and proper for "priests" (i.e. those holding the office of the ministry) to marry.  So, there's a logical connection then that seems to state that those who hold the office of the ministry could, theoretically, hold a civil office.

However, Article 28 (http://bookofconcord.org/augsburgconfession.php#article28) goes into more details about the distinctions between God's Left Hand Kingdom (civil government) and His Right Hand Kingdom (the Church).  Both are instituted by God to care for His world; the Left Hand to enforce order, keep peace, pursue justice; the Right Hand to proclaim the Gospel by which people are saved by grace through faith.

A key quote from this Article is: "If bishops have any power of the sword, that power they have, not as bishops, by the commission of the Gospel, but by human law having received it of kings and emperors for the civil administration of what is theirs. This, however, is another office than the ministry of the Gospel."

The point is that bishops may have their office in the Right Hand realm as well as their office in the Left Hand realm, but that they have to understand that these are separate offices with different roles.  So, the Confessions seem to recognize that the possibility exists for one person to hold both a Left Hand ("secular" or "civil) office and a Right Hand ("spiritual" or the office of the ministry).

That said, is this advisable, even if it is technically allowed?  That's probably a separate question that what was originally asked.  On the one hand, it would be hard for a pastor to separate his office in the ministry with his office as, for example, a mayor.  On the other hand, if a pastor may get married, perform marriages, even serve as a soldier (e.g. a military chaplain), then why can he not serve as a mayor?