How come atheists don't form a political party?

If there is one thing that you keep quiet in politics, it is your religious preference. At least until after the elections anyway. Once you are in power there is not much they can do, but you can show them in the time from then until the next elections that you are a competent enough for the job even if you are an atheist. I wish people would leave religion out of politics all together, after all parliaments and governments ect were not created by "god" but by us humans. Politics is not a religious subject and church should always be seperated from state.