A group of constitutional scholars (39 in all) has written to Congress to answer the claims that it would be unconstitutional for Congress to make the District of Columbia the 51st state, unless that is done by constitutional amendment.
It argued that Congress could do so constitutionally by passing a simple law, as was done with the 37 states admitted since the Founding era.
The letter’s constitutional arguments are well worth reading. It does not attempt to deal with the political issue — that is, the likelihood that the two U.S. Senate seats that would be created for the District would inevitably be won by Democrats. It also does not deal with the fact that, given the filibuster possibility that still exists under Senate rules, the statehood bill would have to be supported in the current Senate by 60 votes.
The text of the letter was distributed by “51 for 51,” an advocacy group supporting statehood. Here is a link to the press release, which includes a link to the text of the letter:
https://www.51for51.org/news/icymi-forty-constitutional-law-scholars-release-letter-to-congressional-leadership-affirming-d-c-statehood-is-constitutional/