The race for the Republican presidential nomination couldn’t possibly get any more bizarre, appalling, puerile, embarrassing, self-destructive or —

Hold on, this just in: It did.

When have we ever seen such a shameful and low-minded spectacle? Comparison to the seriousness and decorum of an elementary school playground is an insult to second-graders. What this campaign needs is a timeout chair, or perhaps a stout wooden ruler for rapping knuckles.

I suppose we have to begin with Donald Trump’s slowness in rejecting praise from former Ku Klux Klan grand wizard David Duke, who announced he will vote for Trump in a rambling, hate-filled Facebook post on Friday that denounced “the Jewish tribalist takeover of our media” and “the crimes [of] Jewish predator banks.”

Trump finally disavowed Duke late Sunday, but only after a day of hemming and hawing. He later claimed that he hadn’t understood the original question, blaming CNN for providing him with an allegedly faulty earpiece.

During appearances on network television Feb. 28, Republican presidential candidate Donald Trump repeatedly declined to refuse the endorsement of David Duke, a former grand wizard of the Ku Klux Klan. While Marco Rubio and Ted Cruz both took aim at Trump. (The Washington Post)

In the meantime, however, his opponents pounced by making clear that they wanted to have nothing to do with white supremacists. The back-and-forth drew attention to the fact that white-power and other nativist groups see Trump as something of a champion — though some leaders, including Duke, wish he were not so supportive of Israel.

That, believe it or not, was the most substantive exchange among the candidates since last Thursday’s debate, when Marco Rubio and Ted Cruz ganged up on Trump in a palpably desperate attempt to keep him from running the table in the Super Tuesday primaries.

Cruz continued to argue what has already been amply demonstrated: that Trump is not an authentic conservative. I’m not sure about the effectiveness of this line of attack. It should be clear to everyone by now that Trump is offering himself as a strongman who transcends ideology. Perhaps what Cruz was really trying to do was shore up his own support in his home state of Texas, where losing could well be fatal to his campaign.

Rubio, on the other hand, frantically tried to out-Trump Trump. The barrage of carefully prepared one-liners began at the debate, when Rubio said, among other things, that if Trump hadn’t inherited a fortune from his father, today he’d be “selling watches in Manhattan.”

Rubio also accused the business mogul of lying, of having no health-care policy, of running a “fake school” that cheated students out of thousands of dollars (the defunct “Trump University”), of taking an “anti-Israel position” in the Middle East — the list went on and on. He mocked Trump’s demeanor and appearance.

Afterward, although such a thing seemed impossible, things got worse. Rubio went into flat-out “yo’-momma” mode.

At a rally, Rubio gave this description of Trump backstage at the debate: “First, he had this little makeup thing, applying, like, makeup around his mustache, because he had one of those sweat mustaches. Then, then, he asked for a full-length mirror. I don’t know why, because the podium goes up to here. . . . Maybe to make sure his pants weren’t wet, I don’t know.”

Republican presidential candidate Marco Rubio took aim at Donald Trump on Feb. 28, criticizing his rival's "small hands" and "spray tan." (Marco Rubio)

Since then, Rubio has said that Trump flies around on “Hair Force One”; ventured that “some would say” Trump is a “lunatic” much like North Korean leader Kim Jong Un; said Trump has “the worst spray tan in America” and “should sue whoever did that to his face”; and called the Republican front-runner a “con artist.”

Trump, of course, responded in kind. This, ladies and gentlemen, is what the Party of Lincoln has been reduced to.

Rubio finished the weekend with this riff, which sounded suspiciously like . . . well, you decide: “He’s like six-two, which is why I don’t understand why his hands are the size of someone who’s five-two. Have you seen his hands? They’re like this. And you know what they say about men with small hands.” Pause for effect. “You can’t trust them.”

Rubio managed to lower himself, and the debate, beneath even Trump’s level. But I’m not sure there was much of a choice. Trump is threatening to effectively lock up the nomination before Rubio even notches his first primary victory.

While Rubio was teasing and taunting, Trump was racking up bombshell endorsements — most notably from ex-candidate Chris Christie, who had vied with Rubio for the votes of establishment Republicans. Christie’s support helps make it safe for others to join the Trump bandwagon; Sen. Jeff Sessions of Alabama climbed aboard Sunday.

Trash-talking, alliances, conspiracies, betrayals — this whole campaign has become a reality-television show. The problem is that it’s on every single channel.

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