I'm not talking about "bidder" for "bitter" or "sidding" for "sitting," or "ladder" for "latter," etc. I'm talking about "Manhaddan," "Pudin," "rodden," "cerdin," "curdin" (for "certain" and "curtain"), and so on.
I first noticed this phenomenon ca. 2010. It seems to be spreading very slowly but steadily since then.
I freely admit I may be wrong (which is why I'm posting this question), but my intuitions tell me it's a vogue phenomenon. For context I should say that I'm almost completely against prescriptivism when it comes to naturally-evolved speech usage, and I can't stand ahistorical linguistic pedantry. But—I will admit to being driven crazy by pretentious ingroup fads. Also, this manner or mannerism itself has the character of pedantry, since the principle is so simple—"Make every glottal -t- into a -d-" and since it is practiced with bizarre, obsessive absoluteness, especially since it's nonstandard pronunciation. In fact, because I'm so aware of it, I'm sure I've heard at least two people flummoxed at overhearing themselves as they said something where the -d- sound actually altered sense—e.g., "I've ridden on cats," rather than "I've written on [the subject] of cats.").
I don't think this is regional—I've known people from California, New York City, and North Carolina who speak this way and have found no particular links in regional migrations, etc.
The only (admittedly soft) connections I've observed are the following.
- Every person I've heard speak this way is under 55, and almost all are 40 or younger.
- Almost all are highly educated—i.e., have graduated from "elite" private schools and colleges.
- Until a year ago, I would've said everyone I'd heard speak this way was a political liberal, but I've now heard people on the right do it, too. (For the record, I'd probably be described as politically left.)
- All the people I've heard speak this way are writers, scholars, intellectuals, professors, pundits, journalists, etc.
A few public figures who speak this way are Ezra Klein, Anderson Cooper, and Katrina Longworth (a film historian).
My questions are: Is this a recognized phenomenon? What is the disciplinarily correct way to describe it? And what is the best way to talk and think about it, with respect to cause?