During the July Fourth week, Barack Obama did something that’s becoming characteristic of his campaign: He took an issue on which he appeared to be vulnerable – in this case the cluster of themes lumped together as “patriotism” – and by going on the offensive in a powerful speech, he subtly changed the terms of the debate.

Obama delivered his patriotism address last Monday in Independence, Mo. (extra points for the campaign scheduler). This might have been the usual cliché-filled verbal waving of the flag, the sort of empty summer exercise that makes American politics so predictable. Such a speech would have reinforced the sense that Obama was on the defensive – that he was doing the rhetorical equivalent of kissing babies and eating corn on the cob in an attempt to placate skeptical voters.

But Obama doesn’t try to please everyone in these situations. When he decides he’s in trouble (and that sometimes takes him a while), he goes to the heart of the matter – into territory that a more cautious and traditional politician would avoid. Knowing that millions of people have seen images on the Internet questioning whether he and wife Michelle love their country, he went at the issue head-on.

“The question of who is – or is not – a patriot all too often poisons our political debates,” he said. Then he laid down his marker: “I will never question the patriotism of others in this campaign. And I will not stand idly by when I hear others question mine.” He went on to paint a picture of his own American story, with personal vignettes that would have done Ronald Reagan proud.

You could almost hear the cheers from a generation of Democrats who have been savaged for their supposed lack of patriotism. They tried so desperately to wrap themselves in the flag – think of poor Michael Dukakis sitting idiotically in that tank in the helmet too big for his head, or the absurdity of John Kerry defending his war record against a Republican who didn’t serve in Vietnam. And here was Obama, not on his back foot but leaning forward pugnaciously and saying: Nobody questions my patriotism! Enough!

The patriotism speech reminded me of Obama’s celebrated March 18 address in Philadelphia on race in America. That came at a time when the Obama camp was reeling because of his long association with his pastor, Jeremiah Wright. The Internet was boiling with footage of Wright railing against the U.S. government, and you could imagine that the Obama campaign might go under – pulled down, as if by a dead hand reaching out from a crypt.

But Obama stepped up to that demon. He didn’t duck the race issue, or sugarcoat it with happy talk, but went right at it, in a way that made you think he could actually solve the problem. “I am the son of a black man from Kenya and a white woman from Kansas,” he said, weaving a narrative that explained who he was – and how he had come to sit in Wright’s church – without apologizing.

The speech produced intense debate, but it lanced the boil. When Wright later made more nasty comments at the National Press Club, Obama had a new chance to distance himself, and the issue began to recede. Jeremiah Wright no longer defines Obama.

What’s impressive about Obama are his political instincts and his toughness. Yes, the man gives a great speech, but that’s not why he defeated Hillary Clinton and is leading John McCain in the polls. He has a superbly disciplined campaign organization that has remained intact and confident, while McCain keeps switching strategists. Obama has mastered Internet politics by building an intense core of support and then letting the spontaneous process of social networking do the rest. David Plouffe, his campaign manager, understands that a modern campaign is an emergent, self-organizing phenomenon.

But Obama’s strategists and handlers wouldn’t make a dime’s worth of difference if the candidate himself didn’t have the gift we saw last week. Take your greatest weakness – the thing people whisper about you by the water cooler – and address it directly, without apologies or sweet talk. That’s Obama’s approach, and in a country where people increasingly seem to regard politicians as professional liars, no wonder people find it refreshing.