PURE SLEAZE…. Last night, Hilzoy tackled the substance of John McCain’s latest TV ad — the one that suggests Obama’s support for giving sex-ed lessons to kindergartners — and explained why it’s breathtakingly wrong.

But stepping back, it’s probably worth putting the ad, arguably the most offensive campaign commercial of the cycle, in the broader context, and consider what it tells us about John McCain.

Asked for a response to the ad, Obama campaign spokesperson Bill Burton issued a statement: “It is shameful and downright perverse for the McCain campaign to use a bill that was written to protect young children from sexual predators as a recycled and discredited political attack against a father of two young girls — a position that his friend Mitt Romney also holds. Last week, John McCain told Time magazine he couldn’t define what honor was. Now we know why.”

That’s clearly the appropriate tone, but Josh Marshall says what the Obama campaign is reluctant to articulate.

[L]et’s not be surprised. McCain is pure sleaze. Sound harsh? Sure. But any other interpretation of the man at this point amounts to willful obliviousness or an embrace of the fantasy that he somehow doesn’t know what his campaign is doing in his name. This is the race he’s decided to run.

The bottom line is straightforward enough: it takes a degree of courage to run an honorable campaign. It takes a degree to integrity to tell voters the truth, present a credible vision for the future, and ask for the nation’s trust.

Cowardice is much easier.

There is a clear strategy emerging for the campaign’s homestretch. The more the McCain campaign comes up with new disgusting attacks and blatant lies, the more the Obama campaign has to respond. To leave attacks unanswered, or obvious distortions unacknowledged, would be a mistake. At the same time, the more time the Obama campaign has to respond to McCain’s sleaze, the less time Obama has for his own message.

In other words, if Obama responds to McCain’s sleaze, McCain benefits. If Obama ignores it, McCain benefits.

Remember, McCain’s own campaign manager conceded last week, “This election is not about the issues.” And the only way to ensure it’s not about the issues is to run nauseating ads like the one the McCain campaign unveiled yesterday afternoon.

I’ve long felt that the challenge of being a good political writer is knowing, or at least learning, how to express an emotional reaction without losing one’s cool. It’s tempting to let one’s frustration out, writing in all-caps, and using every expletive that comes to mind — maybe even making up some new ones — in order to fully convey one’s sense of disgust. But that, in some ways, is too easy. It’s more difficult to convey the same sense of revulsion without flying off the handle.

So, I’ll just say this: John McCain has no business leading the greatest nation on earth.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.