Until recently, American politics was as flat as a backyard swimming pool. This year, the politicians gathered for their quadrennial family cookout, known as the presidential primaries. Suddenly, everyone saw some big old blond guy in red trunks bouncing on the diving board. Uh-oh. Then the big guy launched himself, butt first, into the middle of the pool. Everyone, and I mean everyone, got soaked.

Uncle Don, the uninvited guest at the 2016 election, has upended almost everything we knew about presidential campaigns. Not least is the way Donald Trump talks.

“I would build a great wall. And nobody builds walls better than me, believe me. And I’ll build them very inexpensively. I will build a great, great wall on our southern border and I’ll have Mexico pay for that wall.”

“Get ’em out of here. That’s right. Get ’em out of here.”

Nobody in politics talks like that. It violates what we now call “the political discourse.”

For years, politicians have been oh-so careful with their words. In part, this is the language of constituencies and coalition-building, the constant calibrating of support.

But it is also because in our time the media has made politicians pay a price for saying anything that risks harming this or that collection of political sensibilities. When Hillary Clinton said, “I have a lot of experience dealing with men who sometimes get off the reservation,” the press said she had disrespected Native Americans.

It’s ridiculous, but real. No straighter jacket exists in politics today than language. Marco Rubio, an articulate and often forceful speaker, is careful not to push too far beyond the spin zone.

There is also the fact-checking mania. PolitiFact got a Pulitzer Prize in 2009 for its microscopic fact-checks . . . and the politicians went to ground. Scrupulous exactitude in politics may be a good thing, but it’s also dull.

A century or more ago, “intemperate” wasn’t in the political vocabulary. Compared with Teddy Roosevelt, Donald Trump is Little Bo-Peep. The historian William Leuchtenburg writes that Roosevelt once attacked the Colombians as this “pithecoid community” of “Dagos” and “homicidal corruptionists.”

Possibly we are better off without TR’s red-faced eruptions. The problem today is that fear of offending or losing votes has so blanded out the political class that many of these politicians and the American electorate are no longer speaking the same language.

Into this void flopped a couple of rhetorical throwbacks—Donald Trump and Bernie Sanders. Though both lacked eloquence, people everywhere responded to their blunt language, to the point of being oblivious to its content. It was the way they talked that connected with voters. Messrs. Trump and Sanders liberated their audiences from normal politics, because normal politics had become suspect.

Some argued that Mr. Trump merely tapped into latent anger at political correctness. But Bernie embodied PC. Something else in the culture elevated this new political language.

It isn’t exactly truth-telling, because so much of what these two said remained obscure. Liberal critics pointed out that Bernie’s spending was essentially limitless. The Trump wall, like Jack’s beanstalk, kept getting bigger. It didn’t matter. It seemed—or sounded—so real.

Many people today think food isn’t real unless the label tells them it is organic or artisanal. TV commercials announce, “Not actors, real people.” Politics has no immunity from these new interpretations of what’s real. Just the feeling of authenticity for many has become more powerful than understanding the grubby realities of political limits.

Many voters don’t want to hear established politicians talking about the political process, as Mrs. Clinton is doing now, endlessly. What they want is a fighter, a valiant gesture. The Trump and Sanders detractors thought they were hearing a fascist or a socialist wingnut. Their supporters were hearing Sir Galahad, a knight to the rescue.

The political language of a Trump or Sanders also became a kind of shared code of entry. Only individuals able to speak the new language among themselves could “get it.” The discussions of illegal immigration and income inequality go on inside a kind of impenetrable regional dialect, like the way Donald Trump says China—“Chiiii-nuh!”

Hillary Clinton is the antithesis of the current need. Every word she speaks, because it is so carefully planned, rings instantly false. Even the true ones.

Still, the now-evident limitation of this new emotive political language is that none of its speakers or hearers knows what to do next. What comes after the words remains an unchartered frontier.

Bernie Sanders fell short. The current Trump campaign looks like a game of Twister, covering the blank spots. Even the Clinton camp is wrestling with two words—honest and trustworthy.

In the suddenly tightening presidential race, we are seeing, or hearing, the careful and “reliable” political language of Hillary Clinton in competition with the intemperance of Trumpian rhetoric. One sounds real, the other just doesn’t. The new way of talking in American politics may turn out to be enough to win.