As someone who does it all the time with my divination work, and it's also the reason I took up tarot in the first place, I can safely say it's about as effective as reading for personal querents. My first deck was the Avalon Tarot, which is very good for reading UK politics, with its images of knights, queens and quests for the Holy Grail, and the World card depicts the British Isles.
Politics is just human behaviour writ large, so there is no reason to believe that it takes a special person or methods to do it. If you are interested, by all means go ahead. There is one "election candidate" spread on the spreads board, but it was designed with the 04 US Election in mind. Maybe you can contribute your own spread?
I found a spread I did for my council candidate boyfriend was spot on in terms of the results of his election.
A word of warning though, the mods don't like people discussing politics on the non-political forum (there is one on the subscribers area, but it is hidden from view and I have pledged myself "not to go there").