is the false (plastic) grass used by some stadiums rather than plant real grass for players (ususally football) to play on.

However, in this instance, the definition is that of a attempt by a group to market a position by appearing to be a grass-roots campaign.

(BTW: for the record, sincerity is not an issue as any good advertiser will tell you he is always sincere, regardless of the campaign.)

Okay, so now you have to demonstrate intent to misrepresent.

I'm not claiming that's it's an Astroturf campaign. An Astroturf campaign attempts to look like a "grassroots" campaign - and I doubt anyone will try and claim that 500 form letters represents a "grassroots" campaign.

Oh, and by the way, what is the defintion of "grass roots campaign?"

Generally speaking (and someone can correct me if they wish) a grass roots campaign is a number of people speaking out on a issue without a coordinated effort by someone to get them to all say the same thing.

Such campaigns start very small, and then gain numbers if people agree with what's being said.

My litmus test : a grassroots campaign will tell you the phone number of your Congressman (or whomever) and urge you to contact them. A non-grassroots campaign will produce a letter for you to sign and send to your Congressman. (YMMV)