Yes, for the record, "I understand that Senator Clinton, periodically when she’s feeling down, launches attacks as a way of trying to boost her appeal" is indeed a sexist dog whistle.
Once again, I'll note that the same person who is almost universally regarded as an orator of unrivaled competence, who is heralded as a linguistic maestro gifted with the talent for launching a political movement with the mere power of his well-chosen words, cannot believably claim to not have had the slightest inclination that "periodically feeling down" might be construed as having a double meaning as applied to a female opponent.
Mr. Shakes, who was an early Obama supporter, but whose support has faded in the wake of some of his less-than inspiring rhetorical flourishes, just laughed out loud when I read him the quote and asked if he thought it was sexist. "Obama knows every connotation of everything he says and what it's going to mean to his audience," said Mr. Shakes. "Of course that was sexist. From the barroom to the boardroom, men constantly make 'jokes' just like that about women being nuts when they're on their periods. To believe that Obama did not have a sexist intent is to believe that he is completely unaware of male culture."
Specifically corporate male culture. It's no coincidence Mr. Shakes mentioned boardrooms.
"Periodically feeling down" is the textbook asshole male corporate wanker put-down, the kind of demeaning snipe used incessantly against female colleagues which they can't report without looking like hysterics. Any woman who's found herself in a corporate setting in which there are men who make those little digs at her constantly, suppressing their snide little grins as they throw her under the bus, can spot these dog whistles at a thousand yards, and all of the little snipes Obama uses are of the same tenor—tea parties, on edge, likeable enough, claws come out… He is a classic boardroom bully.
Or he is not at all the firm commander of the English language we imagine, and has stupidly managed to repeatedly stumble into using turns of phrase that sound remarkably like the comments routinely used by sexist bullies in corporate settings after somehow having avoided any awareness of such comments' existence for the entirety of his career.
Paging William of Ockham.
I could be completely off-base here, but my impression is that the precise tenor of this stuff may be lost even on feminists and feminist allies who haven't spent a lot of time immersed in the corporate sphere, where this shit is indigenous and endemic. I'm not suggesting that sexism isn't ubiquitous in academia and elsewhere, too—but perhaps it manifests in a slightly different way. In any case, the idea that calling out this comment as sexist somehow "undermines attempts to point out the extensive and genuine sexist attacks that Clinton has actually received" is something with which I vehemently disagree. This is a genuine sexist attack—one that countless working women must endure day in and day out, perhaps the most pervasive kind of sexist attack there is, and the most pernicious, because so few are prepared and/or willing to see it for what it is.
"Periodically feeling down" makes my teeth absolutely grind. It's the perfectly constructed smear, the tree that falls in the forest and makes no noise—no one really notices, and everyone crushed beneath its weight cannot be heard.