Gin Up

I first heard it from Cokie Roberts during one of her Monday-morning NPR commentaries: Hillary Clinton was ginning up support.

What? I thought. Doesn't ginning up imply (as Oxford Dictionaries says) the use of dubious or dishonest means? From the context, that was clearly not what Cokie meant. Her sentence would have made more sense if she had used whip up support. Gin up would make more sense to me if she had been talking about creating outrage or controversy.

A few days later I heard someone else on MSNBC (maybe Chris Matthews on Hardball) use it as a synonym for whip up yet again. And finally, this morning, Steve Inskeep used it once more on NPR's Morning Edition.

What's up with all this ginning up, anyway?

Checking Garner's Modern American Usage, I found to my surprise that he considers the first definition of gin up to be without connotation: "to rev up (as an engine)," and it's only the second definition that means "to concoct." Garner also points out that it's an American phrase barely mentioned in the Oxford English Dictionary, and that there's a variant gin out, which he rejects.

What's your sense of this phrase? Am I incorrect to hear implied wrong-doing on the part of the "ginner"?
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Here's a nice rumination on the phrase and some of its possible etymologies. Djin? Ginger? Engine? Engineer? So many possibilities, so few facts.