Every ten years, following the Census, states that gain or lose seats in the House of Representatives must redistrict.  Redrawing the boundaries offers opportunities to gerrymander or otherwise create an advantage for one party or the other.  In this cycle, the GOP seems to be ahead of the Democrats in setting up opportunities to pick up seats.  Reid Wilson of The Hill writes:

Republicans appear to be headed for substantial gains in next year's midterm elections, even before many candidates formally declare their plans, as state legislatures and commissions in more than half the U.S. states have proposed or finalized new congressional district lines.

Of those 27 states, a dozen have completed the decennial redistricting process. An additional six do not need to draw boundary lines because they elect a single member in an at-large district.

Those states that have finished or are making progress toward final maps give early hints at the advantages each party has taken as they prepare to battle for control of Congress. 

Republicans appear poised to gain at least one U.S. House seat through the redistricting process in Georgia, Montana, New Hampshire and Wisconsin. And Ohio legislators are contemplating a map that would shift a delegation currently made up of 12 Republicans and four Democrats to one that would favor 13 Republicans and just two Democrats. 

The GOP will lose a seat in West Virginia, where the all-Republican congressional delegation will fall from three members to two.

In some cases, Republican maps that appear to favor more Democratic candidates actually strengthen the GOP's hold on a delegation. In Texas, new maps approved by Gov. Greg Abbott (R) would improve Democratic chances in five congressional districts, and Republican odds in only two seats — but at the expense of five districts that were competitive under old map lines, effectively cementing Republican control of the delegation for a decade to come.

The Democrats have set up some gains as well:

In Oregon, Democrats divided their base voters in Portland across three districts, two of which cross the Cascade Mountains, to give themselves an advantage in five of six U.S. House districts. In Illinois, Gov. J.B. Pritzker (D) is considering a legislature-approved map that would cost the GOP two seats. 

The Maryland legislature, controlled by a supermajority of Democratic members, is considering a plan that would target the state's lone Republican member of Congress, Rep. Andy Harris (R) — a decade after another gerrymander carved up longtime Rep. Roscoe Bartlett's (R) district. (snip)

Maryland's current gerrymandered District 3 (source).

California's independent redistricting commission, tasked with eliminating a seat for the first time in the state's history, offered an initial proposal this week that would give Democrats a big advantage in 38 of the state's 52 districts, and a distinct advantage in five more districts, a likely win for Democrats. That initial map is likely to undergo substantial changes in the coming weeks. 

Democrats are likely to make a play for more seats in New York, while Florida Republicans are likely to press their advantage in a state where Republican registered voters now outnumber Democrats for the first time. Commissions in Virginia and Washington State are hammering out proposals that could affect the balance of power in Congress for the next decade.

This is a decent summary with one major caveat.  In assessing who is gaining or losing from changes in district lines, the analysis is based on voting results in 2020, when, nationally, Dems won the House vote by 3 percent.  Today's Washington Post/ABC poll has the GOP ahead in a generic vote by 10 percent, the biggest margin for the party in 40 years.

In 2014, the GOP won by about 6 percent and had a 247-188 House margin.  At the time, North Carolina and Pennsylvania had district lines heavily favoring the GOP.  Those disappeared after court challenges before 2020.  My guess is that if the national House vote were the same as in 2020, redistricting alone would not give the GOP a majority.

But a decent-sized shift in the overall vote for the House — such as currently is indicated by polls — would almost certainly do so.  The incompetence of the current Biden administration is the best thing Republicans have going for them, and unlike Clinton after the 1994 House wipeout, they are not smart enough or practical enough to change course.

Much depends on how active Trump will be and where he inserts himself into the election.  Clearly, the Democrats want him in.

To comment, you can find the MeWe post for this article here.