Tonight Michelle Obama - the “first lady of grievance,” as GOP opponents have dubbed her - delivers a prime-time speech. What she must do is convince Americans that she and her husband are not what many suspect they are: holier-than-thou radicals with chips on their shouldlers.

You know: They’ve got the Harvard/Central Square blame-America-first thing going. She has it more than he.

I’m an Obama rooter. Yet even I understand the Michelle annoyance. Nobody likes sanctimonious lectures about “mean” Americans from a woman out of Princeton and Harvard Law making $300,000 a year.

There was a joke among reporters sunburned to a crisp yesterday in long, hot security lines outside the Pepsi Center here (with bomb-sniffing canines and rowdy protesters and scores of cops in riot gear). It was: how many times tonight will she assure us that she is, indeed “proud of America?”

That she is indeed Exhibit A in the-only-in-America-is-this possible category? The smart money says dozens of times. At least.

First ladies typically don’t matter much, vote-wise. But Michelle Obama has been pretty much relegated to the I’m-the-wife-and-mother thing since spring because of all this. She could matter - by costing him votes.

Let’s review: In January she delivered a long-winded lecture on the need to achieve - but to a group of already high achieving blacks in Atlanta. Some of them later complained she was condescending.

In Feburary, she told a Wisconsin audience that “for the first time in my adult lifetime, I am really proud of my country.”

She later claimed she was referring to our political process. But everybody knew what she meant.

Asked whether she’d support Hillary Clinton as her husband’s running mate, she replied, less than graciously, “I’d have to think about that.”

She said one pleasure of campaigning was having “the privilege of being reminded just how decent people are.” That assumes she forgot, or never thought people were decent to begin with.

Then there was the infamous Americans are “mean” remark and her assurances that Barack, once elected, would not let us slip back into our old lives of slothful indifference.

What? I realize I’ve just made Michelle Obama sound obnoxious. I don’t, in fact, think so.

There’s a high-minded presumptiveness there, true. But her mistakes are balanced by a no-nonsense honesty rare in politics. In my life she’s the sort of woman I love: blunt, tough, smart, sarcastic, a task-master. She tells her kids to make the beds and her husband to dump the garbage.