Politico addresses a process that happens in each decade, and is coming up soon: reapportioning congressional seats among the states based on population data from the decennial census.
For many decades now, the American population, and therefore political power, has been shifting to the south and west. And the study described in that article indicates that that trend will continue.
There are a couple of anomalies, though. Two Sunbelt states, Louisiana and California, could each lose one seat. I assume the Louisiana situation is tied in to population loss in New Orleans resulting from Hurricane Katrina. California has gone into a relative decline, which I think can be traced in large part to an exodus to neighboring states to seek a lower cost of living, and cutbacks among defense contractors in Southern California.
But, if that happens, it won't put too much of a dent in California's dominance. If you compare it to my current home state of Pennsylvania, California's numbers have skyrocketed over the past century. Based on the 1910 census, California was allocated 11 House seats, while Pennsylvania had 36. After the most recent census, that of 2000, California had jumped to 53, and Pennsylvania had slumped to 19. (If you're interested in more detail on that, the House publishes the historical data here.)
There are at least two major political implications of all this:
All of the states that are large enough to have more than one House seat, redraw their congressional district boundaries after each census. Court decisions from the 1960s onward put stringent requirements on that process, which had been a bit more lax at other times in American history. That always entails a difficult battle in each state legislature, but it's even more of a knock-down-drag-out fight when a state loses representation.
A loss of congressional representation entails a reduction of a state's number of electors in the Electoral College that votes for president and vice president. Therefore, it results in a reduction of a state's clout at both ends of Pennsylvania Avenue.