Say you’re the parent of a fourth grader curious about the presidential campaign. It’s only the election of the next leader of the greatest country in the world.

Your wee one wants to know everything about the political process, how the primaries work, how the two major parties function, even the purpose of the electoral college.

All those things can be explained – perhaps with some difficulty, but still.

But what the heck do you say about the behavior of those running for only the most important job on the planet?

How do you explain the conduct of Republican front-runners Donald Trump and Marco Rubio?

From “The New York Times” yesterday:

“In a span of a few hours across Texas, Mr. Rubio suggested that Mr. Trump had urinated in his trousers and used illegal immigrants to tap out his increasing Twitter messages. Mr. Trump countered by suggesting that Mr. Rubio’s excessive perspiration had no place in the White House and brandishing a water bottle to mock the senator’s chronic thirst.”

Forget a vision for the future. This is a race to the bottom, to see who can insult the other with more vigor and bile.

The drumbeat of contempt continues. From today’s “Times”:

Rubio: “Donald Trump likes to sue people. He should sue whoever did that to his face.”

Trump: “I will address little Rubio. The guy has a fresh mouth.”

From Trump, this behavior is nothing new. Among his greatest hits during this depressing primary season, he criticized a female rival for her looks and insinuated a Fox news anchor was menstruating.

Rubio has apparently decided the only way to slow Trump’s momentum is to join him in the petty parade.

In a separate story yesterday, the “Times” examined how Trump uses his Twitter account to turn his followers into a lynch mob against his perceived enemies. One woman he targeted was attacked online for days. His followers even sent images of her face altered in disgusting ways.

I have some small experience with this kind of cyberbullying, though not at the hands of a politician. A couple of years ago, actor Seth Rogen, apparently unhappy with my negative comment about the movie “Snowpiercer,” sent his 3 million followers for my head.

(Mind you, he’s not in that movie. Full disclosure: I really hated that movie.)

For the next day or so, I was harassed. Several promised they would get me fired from my job.

The righteous Internet mob went away – they found a new target for their outrage, no doubt – but it reminded me about “social media.” It brings out the worst in people.

But you don’t need to go online to see people behaving badly. Just follow the news as we head to Super Tuesday.  We’re seeing the very worst characteristics on display right now as those running for the White House trash each other in the most vicious ways. And none of us seems to know how we got to this day or how to make it stop.