In the Face of Old Testament Studies, I read David Howard’s piece on the Book of Psalms. He said that one view out there is that the Psalms were arranged to communicate a point: that, although Israel had lost her earthly king (the Davidic monarch), she still had her heavenly king (YHWH) to guide her.
This reminds me of the current political scene. Many who voted for Barack Obama expected him to be some sort of Messiah, who would change Washington and work with the other side. But, two years into the Presidency, America is not a paradise, and people who voted for Obama either were disillusioned and did not vote in the 2010 elections, or they voted for the Republicans.
Personally, I don’t expect any human leader to be a Messiah. But some people are better than others, and some policies are better than others. That is why I vote.