There's still a couple years to go until the 2020 census, but new population estimates show power in Congress could continue to shift to the South and the West and away from the Northeast and the Rust Belt.

Using data released Wednesday by the Census Bureau, Virginia-based Election Data Services found that if trends continue through the end of the decade, then Texas could gain three House seats and Florida could gain two. Arizona, Colorado, North Carolina and possibly Oregon and Montana could gain one.

And for all those who gain, there must be some who lose: Illinois could lose two seats while Alabama, Michigan, New York, Ohio, Pennsylvania, Rhode Island, West Virginia and possibly Minnesota could lose one, the study found.

More:U.S. Census Bureau: Idaho population booms; Illinois drops to sixth-biggest state

The Constitution requires that the seats in the House be reapportioned among the states according to the results of the census every decade. The earliest the states would gain or lose seats would after the 2020 election.

Apportionment of the 435 House seats — the figure has been locked since 1941, but is not restricted by the Constitution — is largely a mathematical exercise. Every state gets one seat, and then the remaining seats are doled out based on population.

Recent decades have shown that states in the South and West are growing faster than the rest of the country, and therefore gaining more seats in the House. (Every state gets two seats in the Senate, a compromise designed to balance the power between large and small states.)

The decision about how to draw boundaries for the districts is much more complicated and left to the states. An upcoming ruling by the Supreme Court on a case challenging Wisconsin's map could change the rules for drawing districts if the court bars states from trying to favor one political party over another.

The 2020 apportionment projections are preliminary, said Kimball Brace, president of Election Data Services, a consulting firm that specializes in redistricting and election administration.

"The change in administration and the lack of a census director could have a profound impact on how well the 2020 census is conducted and therefore the counts that are available for apportionment," Brace said.