John McCain didn't utter the phrase "middle class" in debates one and two. He didn't utter it tonight, either.

Instead, he talked about "Joe the Plumber."

Joe, whose full name is Joe Wurzelbacher, is the plumber who asked Barack Obama about tax policy during an Ohio campaign event this week. Wurzelbacher hopes to buy his own business. But, as he explained during their now-famous exchange, he worries that he'd face higher taxes if Obama were to become president.

It's not clear to me that Wurzelbacher really would be worse off financially if all of Obama's plans were implemented. Among other things, he might have a much easier time finding health insurance.

But never mind that. Tonight McCain wasn't courting the vote of Joe the Plumber. He was courting the vote of people like Joe the Plumber. Joe, in other words, was supposed to be a stand-in for Joe Six-pick.

But is he really? If Wurzelbacher would owe higher taxes under Obama's proposals--and, again, I'm not sure he would*--it's because he'd be making more than $250,000 a year. Most Americans make far less money than that. Not coincidentally, they'd actually get a tax cut under Obama's plan.**

You can certainly argue that it's wrong, on moral grounds, to tax wealthier Americans. Wurzelbacher himself seems to think that. And that's a fair debate to have.

On the other hand, if you're not willing to raise taxes on the wealthy, then you either have to raise taxes on everybody else or dramatically cut the government programs--like funding for schools, Medicare, plus aid to states and cities--on which everybody else depends. Neither of those options look too appealing right now.

And that really speaks to the broader issue here. The reason so many people noticed McCain's failure to utter the phrase "middle class" during previous debates is that it seemed emblematic of McCain's agenda. He would provide huge tax cuts for corporations and the wealthy. To help pay for them, he'd slash programs that provide basic economic security to less wealthy Americans.

Joe the Plumber might make out just fine under this scenario, but many more Americans wouldn't.

*Update: TNR reader "dbuck" explains one issue: "a business that takes in $250,000 does not necessarily have under the tax code $250,000 in revenues, nor by a long shot does its owner have under the tax code $250,000 in income. In other words, Joe's potential tax situation is an unknown." And here's the estimable Dean Baker reminding everybody that even if Joe's tax bill would go up, the difference would be pretty modest.

**Update 2: Just to emphasize a point I've made before, I'd actually prefer Obama didn't cut taxes for so many middle class Americans, at least not permanently. But that's another story.

--Jonathan Cohn