THE BEST DEFENSE IS A STRONG OFFENSE…. Realistically, it’s not at all fair to keep expecting Barack Obama to deliver stirring, powerful, historic addresses. Faced with key moments repeatedly over the last few years, the political world seems to consistently wait for Obama with a four-word phrase in mind: “This better be good.”

And yet, he keeps managing to exceed expectations.

It was, by most measures, a different kind of speech for Obama, a fact that did not go by unnoticed. Joe Klein noted, “Barack Obama’s acceptance speech tonight wasn’t what people have come to expect from a Barack Obama speech. It wasn’t filled with lofty rhetoric or grand cadences. It did not induce tears or euphoria.” John Dickerson added, “For a speech before 80,000 people and Doric columns in a football stadium, Barack Obama might have been expected to summon winged chariots, F-14s, and maybe a marching band. When he finished, hats would be cast into the air, and rent shirts would litter the floor. Obama didn’t deliver that speech.”

But those aren’t criticisms. Indeed, Obama deliberately avoided that kind of speech, for a more forceful articulation of why he’s ready to lead, why John McCain isn’t, and precisely what he wants to do for the nation. It’s easy to call for change, so Obama described the kind of change he envisions. It’s easy to condemn an opponent, so Obama explained why McCain’s ideas are intellectually and practically bankrupt.

The result was one for the books. People are going to be talking about last night for quite a while.

Most of Obama’s more memorable speeches are powerful. Last night, he mixed power with persuasion. Listening to the substance and taking in his vision, it was clear this wasn’t about Obama giving his audience goosebumps, but rather, giving his audience a direction, and a reason to follow him. To that end, over the course of 45 minutes, Obama set the campaign on a new course.

It’s tricky to go on the offensive while maintaining an optimistic and inspirational tone, but that’s precisely what made Obama’s speech so effective. He didn’t just take the fight to McCain, he eviscerated McCain, his worldview, his party, and his record. Obama took McCain’s claims and debunked them. He took McCain’s talking points, and mocked them. Remember the questions about Obama’s toughness? His willingness to mix it up? Neither do I.

The speech was also strikingly self-aware. Obama knew exactly what detractors have been saying, and the areas of doubt for voters — Does he have a clear agenda? Is he more talk than substance? Celebrity? Taxes? — and methodically, almost surgically, made his case.

There weren’t a lot of laugh lines or rhetorical tricks last night. Obama was, for lack of a better word, serious. In fact, he called McCain out for doing the one thing presidential candidates shouldn’t do: run an unserious campaign. “The times are too serious, the stakes are too high for this same partisan playbook,” Obama said. “So let us agree that patriotism has no party. I love this country, and so do you, and so does John McCain. The men and women who serve in our battlefields may be Democrats and Republicans and Independents, but they have fought together and bled together and some died together under the same proud flag. They have not served a Red America or a Blue America — they have served the United States of America. So I’ve got news for you, John McCain. We all put our country first.”

As Josh Marshall concluded, “[F]or this moment, John McCain looks very, very small. Both in stature and as a person.”

Game on.

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.