Republicans hold total control of redistricting in 18 states, including Florida, North Carolina and Texas, which are growing in population and expected to gain seats after the 2020 census is tabulated. Some election experts believe the G.O.P. could retake the House in 2022 based solely on gains from newly drawn districts.

Already, Republicans are discussing redrawing two suburban Atlanta districts held by Democrats to make one of them more Republican; slicing Democratic sections out of a Houston district that Republicans lost in 2018; and carving up a northeastern Ohio district held by Democrats since 1985.

“I would say that the national vote could be the same as this year two years from now, and redistricting by itself would easily be enough to alter who controls the chamber,” said Samuel S. Wang, the director of the Princeton Gerrymandering Project. He estimated that reapportionment alone could net the Republicans three seats, and gerrymandering in North Carolina, Georgia and Florida another five seats.