To argue about whether Obama is God's elect and the sovreignty of God seems to me to be a little misplaced (not that these aren't good topics) particularly when talking about Romans 13. Romans 13 is in the context of how the new creation of God, the church of both Gentiles and Jews, are to live as disciples of Jesus. Before the section on the government in ch 13, the believers are told to live free of violent retribution and return good for evil. Following the words regarding the government in ch 13, the church is again told to owe only love to those around them.
The major issue then as I see it, has to do with power. Here the Christian community is asked to give themselves to the power that unifies and is defined by the power of God that loved us while we were still enemies (Romans 5). It is my understanding that our power as believers in Jesus happens as we order our lives in keeping with our real commander-in-cheif, Jesus, thus witnessing to the power of love found in the cross. A power not defined by the powers of the world but the power of the cross.
The church has been coopted for to long in this country by the allure of worldly, political power. We seemed to have learned little from the history of Europe where the church and state were hand in glove committing all kind of atrocities, and from which the witness of the church is still suffering.
In the context of Romans 13, a nation by definition cannot be "Christian". Nations are founded on the power of the sword (and which they are given to use for the good of the people) which is a totally different power base than the cross the church is called to follow. It is this cross we are to take up daily. It is this power which we are to follow. The key question is whether or not the church is allowing itself to be defined here and now by the powers of the world or the power of the cross. Let the power of the cross be that by which we define and organize our lives. Then we will be the witness we are meant to be and will have the basis from which to share our witness to the world. My prayer is that the church will be the church reflecting the true power of the cross in its life together and its witness.