The 2010 losses could not have come at a worse time for Democrats, because Republicans having unified control in many states meant they had a free hand to control redistricting. (The exception: states that rely on independent commissions or other means to determine districts.) The GOP drew aggressive maps that guaranteed their grip on state legislatures for the ensuing decade, including in North Carolina, Florida, Georgia, Texas, Wisconsin, Michigan, and Pennsylvania.
Though Republicans’ state-level advantage has cracked some since Trump took office—because of both a demographic change favoring Democrats and a suburban backlash against his turbulent presidency—it hasn’t crumbled. Democrats have regained about 300 state legislative seats nationwide since Trump’s election, but Republicans retain a 400-seat edge overall. And although the 2018 election of Democratic governors in Michigan, Wisconsin, and Pennsylvania ended the complete GOP control of those states, Republicans still hold all the levers of power in 21 others, including the Sun Belt behemoths of Texas and Florida. Both states are projected to gain congressional seats after 2020, as is North Carolina, where Republicans hold both legislative chambers and where state law denies the governor, the Democrat Roy Cooper, any role in redistricting. (Democrats hold unified control in just 15 states.)
Now the headwinds buffeting Trump and several Republican governors are offering Democrats the same opportunity the GOP seized in 2010: the chance to post big state-level gains in the election immediately before the decennial reapportionment and redistricting.