I have observed a recent trend to pronounce "the" as "thuh" even if it is followed by a vowel (as in "thuh evening.") Is this regional (I live in Alabama) or national? I think it's the latter. And does anyone have an idea about why this has happened? Has the glottal stop become fashionable? Is it typical of an age group?
It is a world wide, common in all English speaking languages, and it is not new. If I were to give you a reason for it, I would say that it originates from the spelling of the word. It is common for people once they know how to read to replace what they know with what they read. Many people with foreign names experience this daily, when friends and strangers try to pronounce their name, the way it is spelled instead of the way it is supposed to be pronounced.
The phenomenon has a name, although it escapes me at the moment.