It's funny how polarized things are that it seems like nobody here has heard of this yet. But I would also say a lot of people on the left still haven't heard of it either.

It refers to 52 states.

Some Democrats are pushing for D.C. statehood and Puerto Rico.

I'm pretty sure D.C. statehood is just illegal as the rules for the capital are built into the constitution. So if possible at all, it'd require at least a constitutional amendment as well as the normal statehood process. That would mean it's pretty much not going to happen.

What should really happen is that D.C. should be expanded to include all the people who work in D.C. that live in Maryland and Northern Virginia. Capital workers weren't supposed to be able to vote for Federal elections by design.

Supposedly a majority of people in Puerto Rico would now want to be a US state. But the reason it has never happened so far is because they'd have to start paying income tax. Taxes in Puerto Rico are really a nice deal and they'd be giving that up. I think polls are fake in general now and polls about statehood in Puerto Rico taken late in election season would obviously be misleading, so it's probably only strongly in favor of statehood around election time.

Anyways, it's really not a big deal compared to other stuff going on now. It wouldn't be in play for this election of course. As a state Puerto Rico would have 6 electoral votes like Iowa. D.C. with current borders would have the minimum of 3 electoral votes.