Senator Kamala Harris compared President Trump to the Wizard of Oz: Behind the curtain, she said on the presidential debate stage, “it’s a really small dude.” Senator Kirsten Gillibrand came prepared to litigate an op-ed Joseph R. Biden Jr. had written in the 1980s. And former housing secretary Julián Castro issued a cutting apparent attack on Mr. Biden’s age.
Yet as the fourth presidential debate arrives, the previous contests offer proof of how challenging it is to translate biting quips into staying power in the polls.
Ms. Gillibrand is no longer running for president, Mr. Castro is at 1 percent in recent surveys, and Ms. Harris, who enjoyed an initial bounce after the first debate when she laced into Mr. Biden’s record on busing — and had T-shirts ready to reinforce her point — now consistently falls behind several other contenders. (Mr. Biden, whose early front-runner status made him the target of attacks, has seen his polling advantage ebb amid campaign trail challenges, though he remains in the field’s top tier.)
The goal of breaking out in a way that alters the dynamics of the race is all the more urgent for most of the candidates in Tuesday’s debate, as they fight for oxygen in a campaign now overshadowed by the impeachment inquiry Mr. Trump faces in Washington.
“You can see they’re grasping for this one line their staff told them would make them stand out in the crowd,” said former Representative Dennis E. Eckart, an Ohio Democrat practiced in political debate prep.
Catchy debate lines alone rarely determine the outcome of a race. But there is a skill to landing the perfect zinger, the kind of quick remark that can reinvigorate a campaign, boost fund-raising, allay concerns about a candidate or even sink an opponent.
Ahead of the CNN/New York Times debate, here is a guide to the art of the zinger, from veterans of the practice.
Focus on the moment, not just on memorizing a line
When debate moderator Bret Baier of Fox News urged civility and substance at a Republican primary debate in 2011, former House Speaker Newt Gingrich wrote down his words, on an “instinct they couldn’t get through the whole debate” without asking provocative questions, he recalled in a recent interview.
And when another debate moderator, Chris Wallace, asked Mr. Gingrich that night whether his campaign was “a mess,” Mr. Gingrich was ready with a reference to Mr. Wallace’s colleague.
“I took seriously Bret’s injunction to put aside the talking points,” he admonished. “And I wish you would put aside the gotcha questions.”
The conservative crowd loved the lashing of the news media, and Mr. Gingrich’s record of debate-stage zingers helped him survive in the race for longer than some political observers initially had expected.
“You have to think about two audiences,” Mr. Gingrich said. “Those who are in the room, and those who are at home. And you’ve somehow got to meet both.”
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The ability to capitalize on real-time developments also helped former Gov. Chris Christie paint Senator Marco Rubio as a scripted creature of Washington during a 2016 primary debate. When Mr. Rubio responded by repeating several times a statement he’d made earlier, nearly verbatim, Mr. Christie noticed — and called him out sharply.
“One-liners are much better when they come spontaneously than when they’re prepackaged,” he said in an interview over the summer. “Most of those pre-canned lines don’t really go over all that well. I think it’s got to be spontaneous. I think it’s got to be something that comes about in the context of what people are hearing.”
Mr. Christie’s campaign was already struggling by that debate, but his lacerating attack helped ensure that Mr. Rubio’s campaign never recovered, either.
But punchy quips carry risk
Mr. Castro tried a similar approach onstage last month when he suggested that Mr. Biden was forgetting remarks he had just made, comments widely perceived as a swipe at the 76-year-old Mr. Biden’s age. Mr. Castro also argued that Mr. Biden was contradicting himself, though it didn’t appear that he had done so.
“If you were watching, you were saying, ‘Oh, Castro’s paying attention, it didn’t look like he struggled to bring it in,’” said Mr. Eckart, who helped prepare Senator Lloyd Bentsen, Michael S. Dukakis’s running mate, for a memorable vice-presidential debate in 1988.
But just as some Republicans have never forgiven Mr. Christie for his savaging of Mr. Rubio, some Democrats thought Mr. Castro had crossed a line — and an important backer pulled an endorsement, a reminder of the risks of slinging zingers at this stage of the primary, when many Democrats are leery of internecine warfare. (Others defended Mr. Castro, arguing that candidates should be able to withstand tough criticism ahead of a possible general election against Mr. Trump.)
“If you go headhunting, you better be very careful who you’re hitting,” said Tad Devine, a veteran Democratic strategist who advised Senator Bernie Sanders in 2016 but is currently unaligned.
Noting that many Democrats feel warmly about candidates like Mr. Biden, he said, “If somebody hits you, you can hit them back hard — everybody’s going to give you latitude. If you’re going to be that tough, if you’re going to launch, that’s a high hurdle to get over with voters.”
One of the most effective debate retorts in modern history was a light line that got President Ronald Reagan’s opponent, Walter F. Mondale, laughing.
“I am not going to exploit, for political purposes, my opponent’s youth and inexperience,” Mr. Reagan said in a 1984 debate, helping ease concerns about his age.
‘Scriptwriters are lousy debate preppers’
Don’t sound overly rehearsed. Do look for opportunities to make a memorable point.
It’s a difficult balance to strike, debate experts acknowledge — and identifying those moments without sounding canned onstage takes practice.
“Most great debate moments are pre-thought-out,” said Karen Dunn, a lawyer and one of the Democratic Party’s most seasoned debate prep experts.
To help prepare Mr. Bentsen to face off against Dan Quayle in the vice-presidential debate, Mr. Eckart watched extensive video of Mr. Quayle. To Mr. Eckart, Mr. Quayle appeared to be channeling the mannerisms of former President John F. Kennedy, a late colleague of Mr. Bentsen’s.
Mr. Eckart said he did the same as he played Mr. Quayle in debate preparations, convinced the Republican would invoke Mr. Kennedy onstage.
“Bentsen just fiercely looked back at me, and he did not want to respond,” he recalled, describing how he goaded the candidate throughout several rounds of debate practice.
But Mr. Eckart was right: Mr. Quayle did compare himself to Mr. Kennedy onstage, and Mr. Bentsen, having responded viscerally to the comparison during debate practice, was prepared with an answer.
“Senator, I served with Jack Kennedy,” Mr. Bentsen said. “I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you are no Jack Kennedy.”
Mr. Eckart, who is unaligned in the presidential contest, sometimes still assists with political debate prep — and he continues to show candidates video of their opponents to get them talking.
“Eventually they say something that you just look at and say, ‘Oh my God, that’s perfect,’” he said. “Scriptwriters are lousy debate preppers. You have to let your emotion and your deep-seated personal beliefs out.”
Debate specialists stress that genuine conviction is the most important aspect of landing a strong debate line. But candidates and their teams get no shortage of suggestions from outside allies, too, Ms. Dunn said.
“Many people will send in their zingers,” Ms. Dunn said. “Sometimes, if it can’t be used in a debate, it might be usable for speeches. If it can’t be used in a speech, at least it will make the debate team laugh.”