Of all the playground rules that still apply to presidential politics, “don’t hit girls” is probably the trickiest. Especially in debates, where “hitting” your rival (not literally, of course) is the whole point.
That’s why so many male candidates have floundered when they found themselves going man-to-man with a female opponent. Most voters don’t like to see women candidates get attacked or patronized by men. And since debates are often the only moments where candidates share the same physical space, the gender dynamics can be more obvious—and more precarious.
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One-liners can go sour. When Clinton ran for the Democratic nomination in 2007, and all the primary candidates were asked to say one nice thing and one critical thing about the candidate standing next to them. Sen. John Edwards went with “Um, I’m not sure about that coat,” drawing attention to Clinton’s pink jacket in a row of dark suits. The moment was clearly intended as a joke, but the voters thought it sounded sexist. Barack Obama fell into the same trap later in that primary, when Clinton was asked about why voters don’t seem to like her. “You’re likable enough, Hillary,” he interjected. It sounded condescending and dismissive, and made voters like her more.