Hillary Clinton is determined to get under Donald J. Trump’s skin at Monday’s debate, and is testing attack lines to try to rattle him.
Mr. Trump is largely shunning traditional debate preparations, but has been watching video of Mrs. Clinton’s best and worst debate moments, looking for her vulnerabilities.
The two candidates are taking vastly different approaches to what is expected to be one of the most widely watched presidential debates since Carter vs. Reagan in 1980. And their divergent strategies reveal how the candidates and their campaigns see the race, their strengths and their opponents’ weaknesses.
Mrs. Clinton has a thick dossier on Mr. Trump after months of research and meetings with her debate team, including analysis and assumptions about his psychological makeup that Clinton advisers described as critical to understanding how to knock Mr. Trump off balance. Mrs. Clinton has concluded that catching Mr. Trump in a lie during the debate is not enough to beat him: She needs the huge television audience to see him as temperamentally unfit for the presidency, and that she has the power to unhinge him.
Mr. Trump, in turn, is approaching the debate like a Big Man on Campus who thinks his last-minute term paper will be dazzling simply because he wrote it.
He has paid only cursory attention to briefing materials. He has refused to use lecterns in mock debate sessions despite the urging of his advisers. He prefers spitballing ideas with his team rather than honing them into crisp, two-minute answers.
With Mrs. Clinton largely devoting the next four days to mock debate sessions and drills in New York, and Mr. Trump hunkering down only on Sunday, here is a scouting report on the two prospects and their training regimens for Monday’s face-off, according to advisers, allies and friends of both candidates.
Preparations
Clinton:
She is mentally readying herself for multiple Trumps: the disciplined opponent who sticks to big themes, the no-holds-barred adversary who goes on the offensive, and the snide antagonist who calls her a “loser” to her face. Her advisers are hurling a host of Trumpian assaults and counterattacks at her to test her responses and adjust them as needed.
Mrs. Clinton is eager to play offense and try to get under his skin, by doing things like calling him “Donald” and questioning his net worth.
Yet she is also testing out whether and how to interrupt Mr. Trump, as she does not want to be seen as pushy and play into gender stereotypes. In practice sessions, she has come across best when she waits to pounce confidently on Mr. Trump for lying or misstating facts, rather than trying to talk over him.
Trump:
He does not like practicing an answer over and over until it is letter-perfect and appropriately brief. But this weekend’s work will be geared to running through questions while Mr. Trump is on his feet and aware of a countdown timer when he is speaking.
His advisers will try to throw him off balance, and measure his response to possible Clinton jabs like “You’re lying, Donald.”
He believes debates are not won or lost on policy minutiae since most viewers will not remember them in an hour. His advisers see it as a waste of time to try to fill his head with facts and figures. Instead, they want him to practice staying focused on big-picture themes (jobs, terrorism, protecting the homeland and closing borders, “Make America Great Again”) rather than picking fights on side issues or taking the bait from Mrs. Clinton.
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Strategy
Clinton:
She has been steady and poised in debate preparations and knows it is critical that she appear cool and collected on stage with Mr. Trump — from the moment they first shake hands to the moment they say good night.
Mrs. Clinton and her advisers have written out dozens of answers, and she has tested some attack lines on the campaign trail to see what might work in the debate. If Mr. Trump expresses admiration for President Vladimir V. Putin of Russia, she is prepared to evoke the hero of the Republican Party: “What would Ronald Reagan say about a Republican nominee who attacks American generals and heaps praise on Russia’s president?” as she recently said.
Advisers want to work on helping Mrs. Clinton get into a groove on stage as quickly as possible. Should Mr. Trump confront her on the private email server she used at the State Department, she should aggressively respond by pointing to his not disclosing his tax returns.
Trump:
His instinct in debates is often to attack and insult opponents, which had an upside during the circuslike primary debates but could be grating during a 90-minute one-on-one debate.
Mr. Trump has a tendency to belittle Mrs. Clinton to the point of rudeness when he is speaking off the cuff, such as by making fun of her for recuperating from her recent pneumonia.
His advisers want him to project optimism about America and his policies while also showing some heat and energy in the right moments to challenge Mrs. Clinton.
Mr. Trump can get bored with both debate preparations and debates themselves. His advisers have been reinforcing the importance of listening and focusing on every word Mrs. Clinton says and looking for ways to counterattack.
He may not like debate preparations, but he is very competitive and wants to vanquish Mrs. Clinton on Monday night. His team has been emphasizing the best ways to win: Do not pick stupid fights with her or with the moderator; explain yourself rather than get defensive; and deliver the answers you want rather than worrying about directly answering the question.
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Mock Debates
Clinton:
She is expected to do at least one timed mock debate this weekend.
She is believed to have more than one person playing Mr. Trump, to prepare her for different possibilities. One debate coach, Karen Dunn, has worked for her or advised her on and off for 16 years and has muscle memory about the candidate’s best and worst moments.
Mrs. Clinton is mindful of the importance of “podium behavior,” as debate coaches call it. She sometimes takes notes while an opponent is speaking; she also looks directly at her opponent at times, which projects confidence. Her aim is to look steady and attentive when Mr. Trump is speaking, and to avoid visibly or audibly reacting to him too much.
Trump:
He prefers not to do a full-length mock debate, and has no set person playing Mrs. Clinton.
He is not using a lectern for mock debate drills, despite suggestions from some on his coaching team that simulating a one-on-one debate is good practice after the primary debates that featured several rivals.
Some Trump advisers are concerned that he underestimates the difficulty of standing still, talking pointedly and listening sharply for 90 minutes. In the primary debates he often receded into the background, and only jumped into the debate forcefully when he was attacked. Some advisers worry that if Mrs. Clinton surprises him, he will be caught flat-footed.
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Strengths
Clinton:
• Dutiful student, quick to absorb information. She limited her campaign schedule after Labor Day to pore over briefing books. Up to speed on all her briefing materials.
• Good self-editing skills. Mrs. Clinton grasps that answers need to be trimmed down to two minutes (and rebuttals should be even tighter) and will keep working to tighten her answers in coming days. Responds well to timers and stopwatches but also has an instinctual sense of time running out.
• Aware that preparations are a relief valve. She vents frustrations during preparation sessions, joking and being sarcastic in ways she never would before a national audience.
Trump:
• Unpredictable. Whether in politics or business, he takes pride in sizing up opponents based on their language, posture, eye contact, and particularly the needs and goals that his adversaries have at that moment. He will hold back, lunge forward, or stay cagey at varying points in hopes of knocking his opponent off balance.
• Studying her strengths and his faults. Mr. Trump has reviewed tapes of Mrs. Clinton’s old debates as well as compilations of his own worst moments during the primary face-offs.
• Self-confident. He has said repeatedly that he can handle Mrs. Clinton on stage.
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Vulnerabilities
Clinton:
• Can appear stiff and irritable under pressure.
• Sometimes packs too many facts into answers.
• Tendency to get defensive about questions involving her honesty and trustworthiness. She has delivered multiple answers explaining her use of a private email server as secretary of state; she is practicing one clear, crisp answer for the debate.
• Hard to predict how she will respond if relentlessly attacked on character issues like her ethics, honesty, and relationships with wealthy donors, or on her husband’s character (such as his past infidelities).
Trump:
• Can be insulting and demeaning to his opponent, the debate moderator, and voters at large, which can be off-putting.
• Tendency to lie on some issues (like his challenge to President Obama’s citizenship) or use incorrect information or advance conspiracy theories — all of which opens him to counterattack from Mrs. Clinton or rebukes from the moderator. Advisers are urging him to focus on big-picture themes rather than risk mangling facts. If Mrs. Clinton says he is lying, his advisers want him to focus on her trustworthiness and issues like her State Department email and accusations of favors for donors.
• Lacks a range of perspectives from women as he prepares to face the first-ever female general election candidate. The only woman consistently in Trump debate preps is Kellyanne Conway, his campaign manager. While she is a savvy and strategic debate coach, Mr. Trump may be underestimating the task of taking on a woman on a big stage.
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Debate Team
Clinton:
Former President Bill Clinton has been attending more preparation sessions lately.
Other regulars include: Ron Klain, a veteran presidential debate coach; Ms. Dunn, a Washington lawyer; Joel Benenson, the campaign’s senior strategist; Mandy Grunwald and Jim Margolis, campaign media advisers; Robert Barnett, a lawyer and friend; John D. Podesta, the campaign’s chairman; and Jennifer Palmieri, the campaign’s communications director.
Trump:
Stephen K. Bannon, the campaign’s chief executive; Ms. Conway; former Mayor Rudolph W. Giuliani of New York; Gov. Chris Christie of New Jersey; Stephen Miller, a policy adviser; Jason Miller, a communications adviser; Lt. Gen. Michael T. Flynn, a retired Army officer; and Jared Kushner, Mr. Trump’s son-in-law.
The former Fox News executive Roger Ailes has not been at the last two debate sessions, but he sends memos and speaks to Mr. Trump.
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Practice Setting
Clinton:
Mostly in New York.
Trump:
Initially at his weekend home in Bedminster, N.J., but moved to Trump Tower in Manhattan after distractions kept popping up in Bedminster.
