Did you happen to notice how, in his masterly mix of reciting and extemporizing, global statesman and Yale Law School graduate Bill Clinton repeatedly inserted the language of back-porch authority into his convention speech? Phrases like, “You all got to listen to this” and “Now think about this” and “You won’t be laughin’ when I finish tellin’ you this”?

Folks, this here was your former commander in chief, taking you by the shoulder, whether you were in the hall or not, and giving you some advice about when to hoot or holler or clap or laugh (or not). His alternation of tone — wryly down-home one minute, charmingly prosecutorial the next — revealed what a useful education in rhetoric politicians can receive when they actually have the opportunity to hone their technique over the decades, from one spotlight moment to another.

The 48-minute speech — an instant convention classic — came just in time. To borrow a phrase from the theater, the Democratic convention was having second-act problems. After the oratorical studliness of night one, when a bill filled by such bracing speakers as former Ohio governor Ted Strickland, San Antonio Mayor Julian Castro and first lady Michelle Obama turned the gathering into an exuberant rally on the subject of the nation’s future, the second night was shaping up to be about as galvanizing as a zoning board hearing on height variances.

And Thursday night, with its marquee turns by Vice President Biden and President Obama, Clinton’s presentation still seemed to resound the loudest — until Obama really got going.

Biden, his voice overloaded with portent, gave a fawning account of his association with Obama, which seemed to go over especially well with a misty-eyed first lady (who sat up front with Biden’s wife, Jill). But the schmaltziness sounded as though the words came from an old movie — “I sat beside him as he made one gutsy decision after another,” he declared — and so the endorsement lacked the consoling illusion of candor.

Obama, true to his nature, was the smoother, cooler antidote to Biden’s unmodulated heat, and in repeating the mantra of auto-industry rehabilitation that has been a convention theme all week, you might say he was wrapping himself fully in the cars and stripes. But the man knows how to build a performance, and, as the speech shifted from rather dreary policy details to the theme of aspiration, the president came into his own.

“If you turn away now, if you turn away, if you buy into the cynicism that the change we fought for isn’t possible, well, change will not happen!” Obama intoned. The speech did not brim with personality, the way Clinton’s did, but it harnessed Obama’s robust star quality.

Despite its agonizing interminability and waning relevance, a national convention still can be a star-maker: the tough-minded Susana Martinez, governor of New Mexico, made a splash in Tampa, and the dashing Castro did the same at the mike in Charlotte. But as with the GOP the week before, far too few of the rank-and-file Democratic speakers seemed as though they could outperform the dullest member of a middling high school debate team. It made me wonder more than once: Why do people with only a rudimentary grasp of how to engage a large audience go into, of all things, politics? And what is the salutary effect on young people watching for the first time — other than to encourage them to go to bed early?

As I did on three nights last week, I sat down this week to a tubeful of conventioneering, to look not so much at the political impact as the degree to which the tools of performance were being used by the parties effectively. This was not an exotic pursuit, for I learned long ago that every political reporter is in part a theater critic; the vocabulary the pundits use on a pivotal night in a campaign is direct from the Broadway manual. “Tonight, we were reintroduced to a star!” gushed the liberal commentator Ed Schultz, on MSNBC, after Michelle Obama’s emotional Tuesday night stemwinder.

Still, as experienced mostly on C-SPAN — the cable outlet for those who want more of the voices onstage and less of the motormouths off — a convention has more time to kill than speaking talent to fill it. (Kamala Harris, the beautiful and highly touted California attorney general, was among those granted a prime-time speaking slot who displayed a need to work a little more on her delivery.)

Maybe it’s simply that formal addresses have little currency in a tweeting nation. And yet, having heard or seen what remarkable orators such as the Rev. Martin Luther King Jr. or John F. Kennedy could accomplish, we all yearn to be swept away by the power of speech. What we’re exposed to more often today are halting, stumbling struggles with teleprompters just out of a television audience’s vision, and irritatingly rehearsed hand gestures that come across as hackneyed stage directions: “For emphasis, press fingers of hand to thumb, and thrust forward. Now, open palms.”

To reinvigorate the art of declamation, it might be time for a new competition series: “So You Think You Can Speak?”

Regardless of how much a political campaign can be reasonably expected to keep such a protracted television event compelling, the two parties were at least trying at times, even inadvertently, to do so. (The roll-call vote has become such a fait accompli the parties wisely shove it into off-hours.) Say what you will about Clint Eastwood’s Albee-esque dialogue in Tampa with The Invisible Man; it made an otherwise bland aspect of the pageant unmissable. And an appearance center stage in Charlotte by Sandra Fluke, the Georgetown law student subjected to offensive characterizations by conservative commentators after trying to speak at a congressional hearing on contraception, provided some intriguingly offbeat casting. It helped, too, that her remarks came across as succinct and polished. “I’m here because I spoke out,” she said, with a firmness that reinforced her reasonableness and sense of conviction. “And this November,” she added, “each of us must speak out.”

The Republicans created a more modern and appealing physical environment around their speakers, a series of 13 screens framed in cherry and mahogany, and each a distinct geometric form. The set looked like no other I’ve seen at a convention, and so you were encouraged in the belief that the gathering might itself be an interesting alternative. The Democrats went for an epic motif, with towering projections behind the podium of postcard American scenes and symbols. This nostalgic imagery and more traditional-looking design seemed reminders of a party in power, given the task of maintaining American might and values.

More important for the viewer at home, the hall in Charlotte, the Time Warner Cable Arena, pulsated more vibrantly than did the convention center in Tampa. The difference might have been that the Democrats simply fill the space with more delegates than the rival party. That paid off in what you might call the crowd scenes. The roars were louder in response to the speakers’ imploring words. When Mark Antony asks for ears to be lent in “Julius Caesar,” the drama tends to be heightened when the Forum is more densely populated.

If the wide hall amplifies exhilaration, the camera funnels warmth, when it detects it. That might be why candidates’ spouses often play so well in convention appearances. Beyond the visceral affection the delegates project in those close-up reaction shots, the mates sometimes manage to reveal some genuine flavor, a magnitude of belief in the candidate that eludes speakers who don’t know the nominee as well — or resort to platitudes that are repeated ad nauseam into the night. By virtue of the delight that she seemed to take in her turn at the microphone, Ann Romney communicated persuasively her faith in her partnership with Mitt. Michelle Obama added an extra measure of writerly know-how, as she drew a link between her husband’s commitment to the nation, and her own commitment to him.

“I can honestly say when it comes to his character, and his convictions, and his heart, Barack Obama is still the same man I fell in love with all those years ago,” she said. She wasn’t beneath a bit of hagiography: describing her husband as hunched over a table at night, reading letters from ordinary citizens, seemed an allusion to another president who engaged in soul-searching epistolary contact with his constituents, Abraham Lincoln. But as Clinton would on the following night, she gave a potent rendition of what’s known in musical theater as the 11 o’clock number — that crucial moment at evening’s end, when the music must ignite the crowd.