There was a lively discussion on the matter here, I reckon about a month ago. You may wish to look it up. I beleive the feeling was mostly that it can't harm. Personally, I think such letters are irrelevant. A politician (or rather - his or her staff) has no standing to testify to your qualities as a researcher, assuming that it's a research of some sort that you do. Nothing can help the case as much as hard evidence, because it's pretty apparent by now that that's what they are looking for.
