- As of this morning, he was not in support of the motion.
- As at this morning, he was not in support of the motion.
Which is correct?
AS of: Used to indicate the time or date from which something starts:
Your second sentence is wrong.
I suppose both are correct. I have heard both used by native English speakers. I prefer the first to the second but that is probably because I am English and the second sentence sounds American, or at any rate not British.