Michael Bloomberg, the billionaire candidate who has bought his way into the 2020 Democratic presidential race, will appear for the first time on a debate stage tonight with the other leading contenders.

The rule changes that cleared the way for Bloomberg’s self-funding campaign to qualify for a place in the Las Vegas debate are frustrating—especially since the Democratic National Committee refused to make adjustments to allow candidates who had played by the old rules, such as New Jersey Senator Cory Booker and former secretary of Housing and Urban Development Julián Castro, to stay in the running. But the former mayor of New York City is now such a presence in the nomination race that he has to be a part of the debate.

They can and should criticize their newly arrived rival; they can and should distinguish where their records and their positions differ from his. But the challenge now for the other Democrats on the stage is to avoid making Bloomberg the center of this debate.

Because if they do make him their focus, they risk handing him a win similar to the wins that Republicans handed Donald Trump when they made him so central to the party’s 2016 conversation and helped him bank endless hours of free media, and in doing so, helped clear his path to the nomination.

The National Public Radio/Marist poll that secured Bloomberg his spot recorded a dramatic spike in support for the candidate who has spent hundreds of millions of his own dollars on sophisticated television, radio, and digital advertising. He’s up 15 points from the last NPR/Marist poll in December. Only Vermont Senator Bernie Sanders is now ahead of Bloomberg, thanks to a nine-point spike in his support, which took him to a commanding 31 percent.

Former vice president Joe Biden is in third place, with 15 percent, down nine points since December. Rounding out the list of candidates participating in the first debate after the Iowa caucuses and the New Hampshire primary, are Massachusetts Senator Elizabeth Warren at 12 percent (down five points from December), Minnesota Senator Amy Klobuchar at 9 percent (up five), and former South Bend mayor Pete Buttigieg at 8 percent (down five, despite top-tier finishes in Iowa and New Hampshire).

Lesser billionaire Tom Steyer is at 2 percent—meaning that he will not be debating, despite the fact that he is campaigning aggressively in advance of Saturday’s Nevada caucuses and next week’s South Carolina primary, while Bloomberg is not.

There is a lot of chaos in the Democratic primary at this point and a good deal of desperation on the part of at least some of the contenders who want to go after Bloomberg when he takes the stage. And there are plenty of avenues for attack, most of which involve the billionaire’s own atrocious statements regarding his “stop-and-frisk” program in New York, his controversial assessments of farmers and workers, his record as a George W. Bush–backing Republican, and his continued funding of Republican candidates in key races as recently as 2018.

But the Democrats who want to go after Bloomberg—because they genuinely disagree with the man and because they see an opening as the anti-Bloomberg contender—should pause and remember 2016.

That year, the leading figures in the Republican Party found themselves running against an interloper from New York who dominated media coverage of the campaign from mid-2015 onward. By March of 2016, when it began to dawn on Republican insiders that their “Never Trump” crusading might not deny the New Yorker the nomination, a study conducted by The New York Times determined that Trump had received almost $2 billion worth of free media.

As CNN explained, this obsessive coverage of Trump was “eclipsing the total value of media attention given to all of his Republican competitors combined.” Indeed, the network noted, “The findings show that Trump earned more than six times as much free coverage as his closest competitor, Ted Cruz, and more than two-and-a-half times as much free coverage as Hillary Clinton on the Democratic side.”

The debates were where the Republican Party—governors, senators, authors, and former presidential contenders—thought it would shred Trump. In debate after debate, they came for him, looking to cast themselves as the “anti-Trump” nominee. The GOP’s “debate partners”—the media outlets that hosted the debates—loved it. Lots of controversy. Lots of clashes over small hands, dismissive nicknames, and fake news attacks.

It was all Trump, all the time. In the first debate, in Cleveland, Ohio, on August 6, 2016, Trump was afforded two more minutes of talking time than the next closest contender, former Florida governor Jeb Bush. And so it went.

Even when Trump was not talking, the other candidates were talking about him. Every time Rand Paul or Scott Walker or Marco Rubio attacked, the moderators turned to Trump. In the desperate days before the first primary in New Hampshire, Texas Senator Ted Cruz and Florida Senator Marco Rubio managed to talk a bit more than Trump, but the billionaire grabbed the headlines when he gleefully “shushed” Bush—after which Politico reported that the son of one former president and the brother of another “stopped talking until Trump was finished.”

By the time the remaining Republicans debated before the critical South Carolina primary in February 2016, Politico announced, “Trump dominates talking time at Republican debate.”

“With the Republican field down to six candidates and the race for South Carolina hanging in the balance, Republicans were desperate to call attention to their campaigns tonight in South Carolina,” read the report, which noted the appearance of “an even cattier version of Trump than we’re used to seeing. He found ways to cut into almost every discussion, calling Cruz a liar, Jeb Bush a failure, and the rest of the field ignorant of his self-professed hard truths. By the final tally, Trump’s butt-ins amounted to a commanding share of the debate; at 15 minutes and 59 seconds, he spoke two minutes more than the next most talkative participant, Ted Cruz.”

Trump and Bloomberg are different candidates with different personas and different strategies. The Democrats who are running against Bloomberg are different from the Republicans who ran against Trump. They are, undoubtedly, certain they can undo this year’s interloper, but that’s what the Republicans thought too.

Of course, Bernie Sanders wants to go after the embodiment of the billionaire class. Of course, Elizabeth Warren wants to take apart the billionaire’s flawed plans. So they should. But if the other Democrats talk too much about Bloomberg and not enough about themselves—about their own ideas, about their own electability—they run the risk of creating a chaos that benefits the candidate with enough money to frame the broader debate. And enough celebrity and controversy to claim his share of free media.

The other candidates should target Bloomberg with thoughtful rebukes and an understanding that he could be derailed or, failing that, that one of them could emerge as the key rival to the surging billionaire. But to succeed, their arguments can’t be Bloomberg, Bloomberg, Bloomberg. To beat the former mayor, his rivals must also amplify their own messages so they are always understood to be more than “Never Bloomberg” contenders.

That’s the lesson of 2016, when a Never Trump candidate eventually emerged from the caucuses, primaries, and debates. He was a skilled debater, with a strong conservative agenda of his own. Yet he focused his energy on a final appeal to prevent the Republican Party from bartering off its future to a scandalous billionaire.

Ask Ted Cruz how that worked out for him.