It's been going on for years.
Used to be the trolls would sign up and immediately post something so obvious, we knew what they were up to. Hence the ZOTS came into play (IBTZ).
Lately though, we now have 'deep cover' trolls, who join, stay as members for a while, then start posting. At first, the posts seem innocuous enough. But, libs being libs, they just cannot help themselves and eventually their lib tendencies begin to show themselves.
I’ve known we have trolls, as you say, they eventually can’t help showing themselves. But the “trollery” I’ve noticed lately has been a bit more subtle-such as the ardent support for McCain, when he’s nobody’s idea of a conservative. I could even understand someone saying they would, if pressed, hold their nose and vote for him as the last resort (though I won’t do even that much), but to enthusiastically support him when there are at least a couple of more truly conservative candidates to consider? I have great mistrust in how he even managed to come in first in New Hampshire-I don’t mean fraud, I mean in who voted for him.