Donald Trump has the sinister ability to make jibes against his opponents that are juvenile, mean-spirited, bullying, and completely beneath the dignity of the presidency—but also effective. On Sunday, during a pregame interview with Sean Hannity that aired before the Super Bowl, Trump directed his ire toward Democratic hopeful Michael Bloomberg, mocking the height of the former New York City mayor while also calling attention to the special dispensation that Bloomberg had received from the Democratic National Committee (DNC) that will allow him to participate in future Democratic primary debates.

Trump invented a lie about how Bloomberg asked for a special box to stand on during the debates, thus combining Bloomberg’s anxiety about his height with the sweetheart arrangement made by the DNC.

“Why should he get a box to stand on?” Trump asked. “Why should he be entitled to that, really? Then does that mean everyone else gets a box?”

Trump’s comments were designed to hit a sore spot. Bloomberg is reportedly 5-foot-7 or, at best, 5-foot-8. He is also sensitive about his height. He once falsely claimed on a driver’s license to be 5-foot-10. On Friday, the DNC eliminated the requirement to have a sizable body of donors in order to participate in the presidential primary debates, clearing the way for Bloomberg, who is using his immense fortune to self-finance his run. While making fun of Bloomberg’s height was cruel, childish, and stupid, Trump’s comments also created a memorable metaphor for the uniquely indulgent treatment Bloomberg was receiving because of his wealth. Bloomberg does, in fact, stand on a special box: one made out of money.

Bloomberg spokeswoman Julie Wood responded to Trump in kind, describing the president as “a pathological liar who lies about everything: his fake hair, his obesity, and his spray-on tan.”

The entire ugly exchange is a preview of what the general election would be like if Bloomberg became the Democratic nominee. The election would be reduced to an insult match between two vainglorious plutocrats trying to unnerve the other with calumny.

These insults are not an accident but go to the heart of Bloomberg’s theory of how to defeat Trump. Bloomberg’s governing idea is that Trump is a fraud, a con man who pretends to great wealth. The way to vanquish a mountebank is by debunking, calling him on his bluff, and deriding his lies. At the Al Smith Dinner in 2016, Hillary Clinton compared Trump to Bloomberg, saying, “I am curious to hear what a billionaire has to say.” The implication being that Bloomberg was the real deal, the authentic billionaire that Trump only pretended to be. Implicit here is the idea that it’s good to be a billionaire.

But there’s another way to criticize Trump: Even if he’s not technically a billionaire, he’s still a very wealthy man, and his policies favor his fellow fat cats. That’s the line of argument that Bernie Sanders and Elizabeth Warren have used against Trump, and it’s also an attack they can use against Bloomberg.

Trump isn’t the only one critical of the DNC for its favoritism toward Bloomberg. Some of the other candidates, including those who have already dropped out, were furious. At a rally in Iowa on Sunday, Michael Moore, a major surrogate for Bernie Sanders, thundered, “I watched the debate in Iowa here two weeks ago—the all-white debate—and the fact [is] that the Democratic, the DNC will not allow Cory Booker on that stage, will not allow Julian Castro on that stage, but they are going to allow Mike Bloomberg on the stage? Because he has a billion fucking dollars!”

Elizabeth Warren sounded a similar note, albeit less profanely. “The DNC didn’t change the rules to ensure good, diverse candidates could remain on the debate stage. They shouldn’t change the rules to let a billionaire on,” she tweeted. “Billionaires shouldn’t be allowed to play by different rules—on the debate stage, in our democracy, or in our government.”

Amy Klobuchar took a different stance. Even before the DNC made its decision, she told MSNBC, “I think that instead of just putting your money out there, he’s actually got to be on the stage and be able to go back and forth so voters can evaluate him in that way.”

Klobuchar’s argument is a compelling one. The fact is, simply by his astonishing spending on advertising, Bloomberg is already having an impact on the race. He’s spent more than a quarter of a billion dollars so far, which is almost 10 times as much money as Bernie Sanders has spent ($26 million). Bloomberg has been steadily rising in the national polls.

Allowing Bloomberg into the debates will allow his rivals to challenge him directly, something they can’t do by advertising, because no one else has anywhere near the war chest Bloomberg possesses. Bloomberg’s participation in the debates would be a genuine godsend to Sanders and Warren.

After all, few figures better illustrate than Bloomberg the dangers extreme economic inequality poses to society. Worth an estimated $61 billion, Bloomberg is by some measures the 14th wealthiest person in the world. He’s used that wealth to gain an outsize voice in public life. Some of the causes he’s taken up, notably gun control and addressing climate change, are admirable. But he approaches every issue as a top-down technocrat—someone seeking to impose solutions on others rather than work with grassroots social movements. He’s also very interested in protecting his own wealth and critical of the wealth tax that both Sanders and Warren advocate.

It’s hard to imagine a more perfect foil for Sanders and Warren, short of fictional oligarchs like Richie Rich, Scrooge McDuck, or “Daddy” Warbucks.

The best role Bloomberg can play in the election is as a stand-in for Trump himself. In the primaries, Bloomberg is well-suited for the Trump role, having the requisite wealth, arrogance, and propensity for personal insult. Sanders and Warren can use him as a foil and hone their debating skills for the confrontation one or the other might have with Trump in the fall.