Whenever you start a sentence "X has a precise meaning", it's uncanny how it always turns out to be the meaning that can be construed most narrowly to support your argument. Reframing what I said to mean an "organized political force behind it"--i.e. the RNC--is a classic example. But let's analyze that.
Whether or not a Republican wrote it, with or without official sanction and/or encouragement, it's been gleefully passed on by, at a reasonable estimate, tens if not hundreds of thousands of Republicans. I'm by no means ahead of the curve: Snopes posted an article dated 3 January 2007, which implies that it went into circulation well before that. It achieved critical mass by early January. It is in every sense of the word a "Republican smear campaign", in fact in the truest sense of the word, it is a grassroots Republican smear campaign. If we accept your claim that it wasn't officially sanctioned, then we can only interpret it as a spontaneous expression of the true beliefs of a great many Republicans.
I don't need to prove it was actually initiated by the RNC or a Republican PAC or a Republican political consultancy. It's a Republican smear campaign.
I dunno if it was a nut typing in a remote cabin (but why assume that Ted Kaczinski was a Republican?). It had been forwarded many times by the time I got it. In classic Republican smear campaign fashion, it's unlikely that anyone will ever be identified as the author. It's just "they say" and "I have it on reliable authority" and, in this case, "Google says".
Speaking of classic Republican smear campaign fashion, it certainly is right down the middle of past Republican smear campaigns. They always play on bigotry and prejudice. Remember the one about Hillary being a lesbian? How about the African American Congressional candidate, Ford I believe, banging white chicks?...
C'mon, do you really want the whole tawdry history of Republican smear campaigns?
To save a little time, let's hop up to the "aside" above.
Do you really think that piece of crap, whatever its source, is going to change the mind of anyone who would have voted for Obama in the first place? It doesn't even make sense when you read it.
Since when did a smear campaign need to make sense?
I already gave the other understood reasons for engaging in a smear campaign, subsumed under the umbrella of "shoring up the base". And as my experience and the Snopes article show, these things never remain within the closed circle of the faithful. They leak out, and among the weak-minded, they sow doubt and uncertainty, and make a few more converts to Republicanism.
I note that you were careful to say "would have voted for Obama in the first place". Can't exclude the large number of who've not yet made up their minds. I'm sure you just forgot that large segment of the electorate.
The logic is exactly like spam: For absolutely no cost (less even than spam, since the faithful can be counted on to do the mailing), millions of people are exposed to the smear. It's profitable if it changes only a handful of minds. There will be many more smears like this between now and November 2008. Each one chips away, tarnishes reputations, and reinforces bigotry and hatred...and not incidentally, contributes to the overall Republican campaign effort.
Quo bono? Absolutely the Republican Party. Quo bono indeed.