CHARLOTTE, N.C. — Democrats opened their convention here on Tuesday night with a parade of officials telling voters that Mitt Romney does not get it and with a rousing speech from Michelle Obama making the case that President Obama does.

Mr. Obama’s roster of Democratic promoters spent the first hours detailing a political indictment of Mr. Romney, blistering him as being out of touch with the middle class and intent on taking the country back to the policies that caused the economy’s problems.

But the main attraction of the evening was the appearance of Mr. Obama’s lead character witness: the first lady, who, wearing a pink-and-gold-speckled sleeveless dress, was greeted with chants of “Four more years!” from the excited arena, to which she responded: “With your help.”

“Barack knows what it means when a family struggles,” she said in remarks that electrified the party faithful in the Time Warner Cable Arena and were broadcast nationally by the television networks. “He knows what it means to want something more for your kids and grandkids. Barack knows the American dream because he’s lived it, and he wants everyone in this country to have that same opportunity, no matter who we are, or where we’re from, or what we look like, or who we love.”