Probably that when the get the big break, they can wreak gerrymandered vengeance on the GOP.
I've thought this for awhile, but it doesn't add up anymore. Michigan has had a GOP-led state legislature for more than 2 decades, save for a Democratic State House from 2007 - 2011. Ohio is very red at the state level and Democrats have basically zero chance of flipping the legislature before 2031.
If this is really their rationale
(it could very well be), then they are idiots. Greedy, corrupt idiots.
If Dems take back the House redistricting reform better be one of the first bills they pass. Independent commissions for every state!
I don't know if that would hold up without a SC composition change and subsequent ruling, but...they could potentially pass legislation that ensures there are independent commissions redistricting every ten years in between the state reapportionment periods as managed by the Constitution; in other words, redistricting every 5 years via 2 different methods.
On the other hand, that might be just as vulnerable constitutionally-speaking as your idea.
I may have misinterpreted what you said, but Congress can pass legislation to regulate redistricting for Congressional districts. They just can't do it for state legislative districts.
It's my hope that Democrats go ahead and do this ASAP, because there is no longer any reason to try and hold out in the off chance they win back mucho state governments - It's just not going to happen anytime soon. The South is mostly gone and it's unlikely (imo) that rust belt states like Michigan would be flippable in time for 2021-2022.