Dave Wasserman from Cook Political Report:

The power shift from the Frost Belt to Sun Belt and western states is a familiar trend. But even states without a gain or loss will have to redraw lines to adjust for population changes in time for 2022 (except the six states with only one district). 

Republicans have the final authority to draw congressional lines in 187 districts, down from 219 seats in 2011. Democrats will have final authority in states totaling 75 districts, up from 44 in 2011. New bipartisan commissions passed by voters in Colorado, Michigan and Virginia bring the number of commission-drawn districts to 121 up from 88 ten years ago. And there are 46 districts in states where control is split between the parties, down from 77.

Republicans’ biggest redistricting weapons are Texas, Florida, Georgia and North Carolina – and they could conceivably pick up all five seats they need for the majority from those four alone. Meanwhile, Democrats’ most prized states are Illinois and Maryland. The biggest wild cards? New York and Ohio, where lopsided state legislatures could conceivably ignore new reforms and impose deeply partisan gerrymanders.

But already, there are some plot twists. Earlier this month, Oregon’s Democrats relinquished exclusive authority to redraw maps in a deal struck to end legislative stalling tactics by the GOP minority — a deal that could cost Democrats at least one House seat.