In a paragraph, I come upon the below sentence.

In fact, independent business alliances across the U.S. are predicting that buy-local movements will make as big of an impact as buy-organic movements have in recent years.

The problem is that I cannot figure out what's the purpose of "of."

The sentence seems OK without "of," so I checked out with GOOGLE to find out the below sentence.

Yet most of that cool stuff hasn't had as big an impact as it might have.

OK. the sentence in question can be OK without "of."

But I still don't know for what the "of" was used.

Could you give me a help?

(Example sentence would be greatly appreciated. Thanks in advance.)
How big of a serving would you like?

He's as much of a jerk as I've ever met!

I've heard these things all my life, but they always seem to come from the "uneducated."

(Native speakers, nonetheless.) Emotion: nodding

As far as I know, the "of" has no function, and should be deleted.
Thanks, Avangi.
Students: Are you brave enough to let our tutors analyse your pronunciation?

I agree with you and Avangi - the "of" should be left out

But in answer to your question - why do people say that?..

I think it is a confusion between "much" and "big". For example..

- He came into my bar and caused much trouble

- He came into my bar and caused big trouble

From the first sentence, you may have..

- OK, he came into your bar, looking for trouble. How much of a problem was that?

- It was as much of a problem as I could handle on a busy Saturday night

This is ordinary English: the "of" goes naturally with the "much"

Some might use the same form with the other sentence..

- OK, he came into your bar looking for trouble. How big of a problem was that?

I can see where the form of that sentence comes from, but I'd say that it is wrong. You can certainly use "of" with "much" but it doesn't sound at all good with "big"

But I believe that explains where the "of" comes from

Best regards, Dave
I agree with you, Dave.

I toyed with discussing the difference between "big" and "much," but couldn't quite get a handle on it.

Well done.

Still, I feel that "He is so much a gentleman that he accepted the insult gracefully" is much "higher register" than, "He is so much of a gentleman that etc."

I guess "so much" and "how much" work a bit differently.

- A.