When I was at MIIS, a friend of mine taking a linguistics class asked how often I replace “going to” with “gonna,” and I said always. But then he brought up the difference between “I’m going to drive to the store” and “I’m going to the store” and taught me something that of course I knew instinctively: “gonna” can only replace “going to” + verb. When “going to” is followed by a noun, you can’t say “gonna” – you can only abbreviate it to “goin’ to” (which I do). Stuff like this fascinates me.
I’m sharing this now because I just read a pretty good article comparing Obama’s and McCain’s use of “g dropping”: