I remember the first time I used the joke. I thought it was amazingly funny and would put my worst enemy in his place for good. But I had to wait for just the right time. It was at recess. We were standing in line to play four-square. He smirked and called me “barf-bag” (it was his favorite name). I looked right in his eyes and said, “You should sue whoever did that to your face.” And for the rest of the day, I was the toast of the second grade.

So, imagine my surprise when I heard presidential candidate Marco Rubio using the

same joke with Donald Trump after accusing him of “riding around in Hair Force One.” I felt proud (though I’m not sure how he heard about my joke all these years later), but also a little bit miffed. He should have quoted me. It was my joke.

Rubio's remark has a context, of course. It comes after Trump dissed Rubio for “sweating like a dog,” causing the Florida Senator to intimate that the casino magnate might have wet his pants at a debate. After these exchanges, the Republican presidential primary now officially has more in common with a second-grade playground brawl than with an actual political contest. We are only days away from the candidates dropping “yo mamma” jokes on the national stage.

Meanwhile, the rest of us are trying to pick a president, and a lot of us are looking for grown ups. The debates on the other side of the aisle, while by no means stellar, have occasionally resembled mature discussions of ideas. At the very least, Senator Clinton has respectfully declined to ask Bernie Sanders if it hurt the last time he fell off a dinosaur, and Senator Sanders has yet to try to snap Hillary's bra strap. At this point, the little things must give us hope.

But our political discourse is still a long way away from the kinds of debates and public appearances that could actually advance the discourse of ideas. The high-water mark for this kind of debate, of course, occurred in 1858, when Abraham Lincoln and Steven Douglas squared off for seven direct debates with each other in their race for the Illinois Senate. These were not the joint press conferences of today. There was no moderator asking questions. They each spoke for an hour and a half and addressed the points that the other made.

And the audience really learned where Lincoln and Douglas stood on the only issue that mattered in 1858, which was slavery. Throughout the debates, Lincoln and Douglas presented and refined their positions. Douglas believed in the principle of “popular sovereignty,” which said that every state and territory should decide where it stood on the question of slavery, and the federal government should honor that choice. It was a delicate dance that had preserved the Union for the past ten years. But it was unsustainable.

Lincoln at the time was no abolitionist. He believed in containing slavery where it already was. But he subtly shifted the debates to the moral plain by arguing that slavery was morally wrong, and that certain policy implications flowed from that acknowledgment. When Douglas refused to admit that slavery was a moral evil, he drew a sharp line between his positions and Lincoln’s. Consequently, everyone who listened to or read the debates understood exactly what the two candidates believed and how those beliefs would affect their actions.

The Lincoln-Douglas debates were a shining moment in our history because the candidates actually found a way to disagree with each other productively—to clarify what the essential differences were in their positions. This is probably an impossible standard to hold modern candidates to.

But there was another aspect of the Lincoln-Douglas debates that we can expect them to emulate: these were contests of ideas between two people behaving like actual adults. Even if we decide not to hold politicians to the “ideas” thing, we can still insist on the “adults” thing. Douglas did not joke about Lincoln’s big ears or ungainly height. Lincoln did not make any cracks about Douglas’s weight or his drinking habits. And nobody pulled anybody’s hair or said, “I know you are but what am I.”

We are well beyond talk of civility and respect for others. Those are things we haven’t seen in years. We are now missing that baseline level of dignity and self-respect that allows people to function minimally in adult society.

And ultimately we are to blame. If politicians like Trump and Rubio were punished at the polls every time they acted like second-graders on the playground, they would either stop doing it or get out of the race. But that’s not what happens. The juvenile behavior is working. It has launched one candidate to the top and appears to be propelling the other into the coveted position of the chief rival. Like second-graders everywhere, we are rewarding terrible behavior by turning the worst-behaved candidates into the popular kids.

And this bodes ill for our country if one of them should win the election, as neither ISIS nor Vladimir Putin particularly cares what an American president thinks of their mothers.