Why don't Democrats sue to challenge the constitutionality of the Reapportionment Act of 1929?
The Constitution explicitly states one representative per 30,000 residents.
The Reapportionment Act of 1929 permanently capped the number of House seats at 435. There was no Constitutional amendment codifying this, so the law is technically unconstitutional. And due to the nature of seat division and small state populations, representation can range from 500,000 to 900,000 constituents per seat, often creating another advantage for small states with populations below the average division.
If we remove the cap and return to the letter of the law (1 representative per 30,000 citizens) the House would balloon to over 10,000 members. The disproportionate small state advantage in the Electoral College and even the House will be mostly nullified, since electors are equal to the sum of House + Senate seats.
While this may make the House unwieldy and difficult to manage, they can find ways to make it work practically via rules and procedural changes.
If they want to "fix" the crowded House, they need to amend the Constitution which requires a 2/3rds majority, and we can make Electoral College reform a condition of supporting any change.
Why hasn't critics of the Electoral College challenged this law yet? It seems to be the easiest way to avoid outcomes like 2000 and 2016 where the popular vote loser wins on a technicality because they won more places that were disproportionately represented.
Side note: I find it hilarious talking to Republicans about the Electoral College. It seems like they finally found a good reason for having disproportionate minority representation on something, and shriek that if we eliminate it, the republic will die and we will have tyranny of the majority (i.e. they will lose their DEI for farm states that benefits them politically in Presidential races.)