The Wyoming Rule is a proposed change in the way that seats are apportioned to the United States House of Representatives. As it is, congressional districts are defined by dividing a fixed number of seats (currently set at 435), by the entire population of the country. For most states, this gives a district size of around 650,000 people. However, each state is entitled to at least one representative, no matter how small its population drops. Thus, Wyoming, with a population of 515,000 people, has one representative, just like Montana, with 950,000 people. Some feel that this violates the purpose of the House, which is to give states equal representation based on population.
The Wyoming Rule would make it so that a house district would be defined as being equal to the smallest unit that gets a house district, which is currently the state of Wyoming. This would increase the number of house seats, perhaps by a quarter or a third. It would probably give more representation to larger, more urbanized states.
Despite the fact that the idea behind the Wyoming Rule does have some good logic to it, since the House is supposed to be representative of population, I can't imagine the political situation where such a bill would be passed. Although conservative versus liberal politics would be one reason for the bill not to pass, there are many other logistical problems with it, starting with the amount of expansion that would need to be done in Washington, D.C. to accommodate more legislators and their staffs. The Wyoming Rule could become a more active issue if the disparity in state population grows larger, but for now it is probably only theoretical.