A SCRAPPY KID FROM SCRANTON…. The political world has certain expectations about the kind of speech a vice presidential nominee is going to deliver at his or her convention. It’s going to be polished, there will be a few clever turns of phrase, and there may be some call-and-response thrown in for good measure.

Joe Biden’s speech last night didn’t follow the script, literally or figuratively. It had a certain fly-by-the-seat-of-his-pants quality, based on Biden’s assumption that he could just say what’s on his mind, and it’d be just as good as what the speechwriters put in the teleprompter. And as it turned out, he assumed correctly.

In all likelihood, no one will ever tell tales of Biden’s oratorical skills, but under the circumstances, it doesn’t much matter. Biden came across as earnest, honest, and sincere. He was likable. He made a powerful argument based on substance, but did so with the kind of raw emotion we very rarely see in speeches from candidates for national office.

In terms of the substance, Biden had two principal high points. First, on domestic policy, Biden demonstrated, with pure populism, that the Democratic ticket understands full well the challenges facing middle-class families: “Almost every night, I take the train home to Wilmington, sometimes very late. As I look out the window at the homes we pass, I can almost hear what they’re talking about at the kitchen table after they put the kids to bed. Like millions of Americans, they’re asking questions as profound as they are ordinary. Questions they never thought they would have to ask: Should mom move in with us now that dad is gone? Fifty, sixty, seventy dollars to fill up the car? Winter’s coming. How we gonna pay the heating bills? Another year and no raise? Did you hear the company may be cutting our health care? Now, we owe more on the house than it’s worth. How are we going to send the kids to college? How are we gonna be able to retire? That’s the America that George Bush has left us, and that’s the future John McCain will give us.”

Looking abroad, Biden slammed McCain repeatedly for his poor judgment on everything from Iraq to Iran to Afghanistan to international diplomacy: “Again and again, on the most important national security issues of our time, John McCain was wrong, and Barack Obama was proven right.”

After Biden’s well-received speech, Barack Obama made a “surprise” appearance alongside his running mate. There was a chance Obama’s arrival would step on Biden’s remarks, but it offered an opportunity to get their picture on the front page together. If for no other reason, it was a good idea.

Ultimately, Biden struck me as a genuine guy with a few endearing rough edges. If Americans watching at home didn’t connect with him, I’d be very surprised.

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.