I have seen it argued here that it requires 60 votes in the Senate. But when I researched it, the Net indicated that all that is required is simple majorities in both houses of Congress. Now the District of Columbia complicates the matter in that it is spelled out in the Constitution its status, which could complicate the matter. However, with the Robert's court, I would not trust that ninny no how!!!
Puerto Rico in my humble opinion would be an easier feat to make a state. I think the Democommies are trying for the tough one first, testing their power, which I believe will make the effort of approving the PR much easier.
But that pendulum can swing both ways. Should the Republicans capture everything, I would not be surprised to see California broken into 2 or 3 states, with the new states conservative. The eight counties in the northern part of California are solidly conservative. One state for sure, perhaps two.
And if new states can be created, existing states can be merged. I say merge Delaware into Maryland or Pennsylvania. Merge Rhode Island into Connecticut or New York. Merge New Mexico into California. Yes, a lot of games can be played by both parties. Question is, do the Republicans have any backbone to play? Doubtful. The Republicans remind me of the individual sitting in a wheel chair at the nursing home, catatonic to the world. Yes, just that much life!!! Trump tried to infuse energy into the party, but all he got from the party leadership was resistance. Pathetic!