In Texas, North Carolina, Ohio and Georgia, Republican state lawmakers have either created supermajorities capable of overriding a governor’s veto or whittled down competitive districts so significantly that Republicans’ advantage is virtually impenetrable — leaving voters in narrowly divided states powerless to change the leadership of their legislatures.

Although much of the attention on this year’s redistricting process has focused on gerrymandered congressional maps, the new maps being drafted in state legislatures have been just as distorted.

And statehouses have taken on towering importance: With the federal government gridlocked, these legislatures now serve as the country’s policy laboratory, crafting bills on abortion, guns, voting restrictions and other issues that shape the national political debate.

“This is not your founding fathers’ gerrymander,” said Chris Lamar, a senior legal counsel at the Campaign Legal Center who focuses on redistricting. “This is something more intense and durable and permanent.”