这是一个特点美国选举过程:总统辩论。
数百万人收看这一历史悠久的传统节目，这一直被认为是寻求执掌美国最高职位的候选人的终极展示。
“这是我们唯一一次看到他们并排在一起，”阿克伦大学政治传播教授米切尔·麦金尼说。“它们为候选人提供了自助或自残的机会。”
让我们来回顾一下美国政治史上一些最难忘的辩论时刻。
尼克松在冒汗
历史上第一次全国电视辩论的主角是约翰·肯尼迪和理查德·尼克松。画面并没有对尼克松有利，因为他在之前因感染住院后大汗淋漓，脸色苍白，而肯尼迪看起来年轻，表现得更有活力。
内华达大学传播学教授雅各布·汤普森说:“有很多猜测认为，尼克松没有考虑到外表的重要性，导致了他在辩论中的失败，进而导致了选举的失败。”
福特的“苏联统治”错误
现任总统杰拉尔德·福特在与民主党人吉米·卡特的大选辩论中犯了一个严重的错误。
福特断言在他的领导下“没有苏联统治东欧”，这句话促使主持人问道，“对不起，什么?”在辩论中，福特对他的回答加倍，尽管后来他说他的意思是共产主义控制下的东欧人的精神没有被摧毁。
“他说的不是真心话，但伤害已经造成了，”休斯顿大学的政治学家布兰登·罗廷豪斯说。
里根拒绝回答年龄问题
罗纳德·里根，当时最年长的在任总统，在与民主党人沃尔特·蒙代尔的辩论中，拒绝回答一些关于他年龄的问题。
“我想让你们知道，我不会把年龄作为这次竞选的一个议题。我不会为了政治目的利用我对手的年轻和缺乏经验，”里根说，引起了房间里甚至蒙代尔的笑声。
“蒙代尔后来在他的传记和一部纪录片中说，你可以看到他在舞台上笑，但他自己脑海中真正发生的是他哭了，因为他知道他已经输掉了辩论，很可能输掉了选举，”汤普森说。
你不是杰克·肯尼迪
在这场副总统辩论中，在奎尔援引肯尼迪之后，劳埃德·本特森猛烈抨击詹姆斯·丹·奎尔。当时，奎尔被拿来与已故总统比较，因为两人就职时都很年轻。
“我和杰克·肯尼迪一起服役，”本特森说。“我认识杰克·肯尼迪。杰克·肯尼迪是我的朋友。参议员，你不是杰克·肯尼迪。”
杜卡基斯的禁欲主义
民主党人迈克·杜卡基斯因对1988年关于死刑的辩论问题的强硬回应而受到广泛批评。
美国有线电视新闻网的肖伯纳引用了一个涉及杜卡基斯妻子的生动假设——但州长在他的实事求是的回应中没有错过任何一个节拍。
"州长，如果基蒂·杜卡基斯是被奸杀的，你会赞成对凶手处以不可撤销的死刑吗?"肖问道。
“不，我不知道，伯纳德，我想你知道我一生都反对死刑，”杜卡基斯回答道。
注视着眼色、叹息
老布什总统在1992年与民主党候选人比尔·克林顿和独立候选人罗斯·佩罗的三边辩论中因低头看表而受到批评。
在一名观众提出一个关于国家债务如何影响每一位候选人的问题后，布什看了看自己的手腕。
2000年，民主党人阿尔·戈尔在与乔治·w·布什的辩论中发出可闻的叹息声，以及在辩论中他决定走过去站在布什面前，都遭到了嘲笑。
里克·佩里的《哎呀》
在2012年共和党初选辩论中，时任德克萨斯州州长里克·佩里(Rick Perry)忘记了一个问题的部分答案，该问题涉及他取消三个联邦机构的计划。
佩里说出了两家机构的名字，但不记得第三家了，他说:“哎呀。”
罗廷豪斯目前正在撰写一本关于佩里的书，他说，这一时刻“实际上是佩里竞选活动的丧钟，当时佩里竞选活动一直萎靡不振，但后来正式死亡。”
克里斯蒂对卢比奥
在2016年的共和党初选辩论中，佛罗里达州参议员马尔科·卢比奥受到了时任新泽西州长克里斯·克里斯蒂的攻击，因为他在辩论中一再使用类似的台词。
卢比奥一再表示，时任总统巴拉克·奥巴马“完全知道自己在做什么。”
“在那里。就在那里。记忆中的25秒演讲。大家注意了，”克里斯蒂一度说道。
克里斯蒂在2024年再次竞选总统，但在第一轮初选投票前退出了，他说，这一时刻摧毁了卢比奥的竞选活动-卢比奥已经明显回击了这一活动。
2020年民主党初选辩论
McKinney说，在最近的民主党初选辩论中，有两个时刻非常突出，第一个是参议员伊丽莎白·沃伦与迈克尔彭博的对决。
沃伦说:“我想谈谈我们的竞选对手是谁:一位称女性为‘肥婆’和‘马脸女同性恋’的亿万富翁。”。“不，我不是在说唐纳德·特朗普。”
沃伦说，她不认为民主党应该“用一个傲慢的亿万富翁代替另一个。”
McKinney说，另一个亮点是卡玛拉·哈里斯在种族隔离和公共汽车问题上对乔·拜登的挑战。哈里斯质疑拜登过去与两名种族隔离主义议员的工作关系。
哈里斯说:“加利福尼亚有一个小女孩，她是整合公立学校的第二批学生中的一员，她每天乘公交车上学，那个小女孩就是我。”。“我要告诉你们，在这个问题上，这不可能是民主党人之间的智力辩论。我们必须认真对待它。我们必须迅速采取行动。”
拜登-特朗普大选辩论
美国总统乔·拜登(Joe Biden)和前总统唐纳德·特朗普(Donald Trump)的辩论最终改变了2024年大选的进程，此前拜登的糟糕表现加剧了民主党和选民对他的年龄和健康状况的担忧。
辩论结束后，要求拜登退出选举的压力持续了数周。24天后，他宣布退出竞选。
对决在6月举行，成为有史以来最早的大选总统辩论。
拜登因感冒而发出刺耳的声音，加上他无法在关键的民主党问题上打击特朗普，在辩论中脱颖而出，特朗普避开了他的一些更夸张的说法。
辩论会改变选举结果吗?
辩论时刻是否会改变选举结果，这个问题本身已经争论很久了。
专家表示，奖学金显示，辩论通常不会改变结果，不足以对最终哪个候选人赢得或输掉比赛产生重大影响。
罗廷豪斯说:“辩论充其量只能起到推波助澜的作用，就像1960年和2000年势均力敌的选举一样。”。“所有这些时刻都被打断，而且选举势均力敌，最终，辩论的作用比传统意义上的稍大一些。”
专家说，辩论在拜登竞选中发挥的巨大作用有点异常。
“有些时候，辩论确实很重要，可以改变比赛的进程，但这很少发生，”罗廷豪斯说。
汤普森说，关于总统辩论的社会科学数据中有两个强烈的迹象，第一个是选民从中学习，第二个是初选辩论的教育和偏好效果远远高于大选辩论。
汤普森说:“初选辩论确实有很大的影响，因为人们对候选人的看法不那么确定，同时党派偏见也不那么重要了。”。
汤普森还指出，初选辩论是重要的，因为它们往往会对总统候选人产生“扬场效应”。
“人们会因为糟糕的表现而退出竞选，或者糟糕的表现导致他们的平均投票率和竞选捐款减少，”他说。
Memorable moments from political debates past
It's ahallmarkof the American electoral process: the presidential debate.
Millions of people tune into the time-honored tradition, which has long been considered the ultimate showcase for candidates seeking to hold the nation's top office.
"Those are the only times we see them side-by-side," said Mitchell McKinney, a professor of political communication at the University of Akron. "They provide opportunities for candidates to either help themselves or hurt themselves."
Here's a look back at some of the most memorable debate moments in U.S. political history.
Nixon's sweating
The first nationally televised debate in history featured John Kennedy and Richard Nixon. The visuals did not play in Nixon's favor, as he was seen sweating and looking pale after previously being hospitalized for an infection, while Kennedy looked young and gave a more vigorous performance.
"There's a lot of speculation that Nixon's failure to account for the way that appearance mattered led to his failure in the debate and hence the election," said Jacob Thompson, a communications professor at the University of Nevada.
Ford's "Soviet domination" blunder
Incumbent President Gerald Ford made a critical mistake during his general election debate against Democrat Jimmy Carter.
Ford asserted there was "no Soviet domination of Eastern Europe" under his leadership, a remark that prompted the moderator to ask, "I'm sorry, what?" Ford doubled down on his answer during the debate, though later said what he meant was that the spirit of Eastern Europeans under communist control were not crushed.
"He didn't mean exactly what he said, but the damage was done," said Brandon Rottinghaus, a political scientist at the University of Houston.
Reagan shuts down age questions
Ronald Reagan, the oldest sitting president at the time, shut down some questions about his age during his debate with Democrat Walter Mondale.
"I want you to know I will not make age an issue of this campaign. I am not going to exploit for political purposes my opponent's youth and inexperience," Reagan said, prompting laughter from the room and even from Mondale.
"Mondale said in his biography later and in a documentary that you could see him on stage at that point laughing, but what was really happening in his own head was that he was crying because he knew that he had lost the debate and probably lost the election," Thompson said.
'You're no Jack Kennedy'
In this vice presidential debate, Lloyd Bentsen tore into Dan Quayle after Quayle invoked Kennedy. At the time, Quayle was drawing comparisons to the late president given both were young when assuming office.
"I served with Jack Kennedy," Bentsen said. "I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy."
Dukakis' stoicism
Democrat Mike Dukakis was widely panned for what critics said was a steely response to a 1988 debate question about the death penalty.
CNN's Bernard Shaw invoked a graphic hypothetical involving Dukakis' wife -- but the governor didn't miss a beat in his matter-of-fact response.
"Governor, if Kitty Dukakis were raped and murdered, would you favor an irrevocable death penalty for the killer?" Shaw asked.
"No, I don't, Bernard, and I think you know that I've opposed the death penalty during all of my life," Dukakis responded.
Watch glances, sighs
President George H.W. Bush was criticized for looking down at his watch during the 1992 trilateral debate with Democrat Bill Clinton and independent candidate Ross Perot.
Bush was seen glancing at his wrist after a question posed by an audience member about how the national debt personally impacted every candidate.
In 2000, Democrat Al Gore was mocked for his audible sighs during his debate with George W. Bush, as well as his decision to walk over and stand in front of Bush at one point in the debate.
Rick Perry's "oops"
In a 2012 Republican primary debate, then-Texas Gov. Rick Perry forgot part of the answer to a question about his plan to eliminate three federal agencies.
Perry named two agencies but couldn't remember the third, saying "oops."
Rottinghaus, who is currently working on a book on Perry, said the moment "was effectively the death knell of the Perry campaign, which had been languishing at that point but then was officially dead."
Christie vs. Rubio
In a 2016 Republican primary debate, Florida Sen. Marco Rubio was attacked by then-New Jersey Gov. Chris Christie for using a similar line over and over again throughout the debate.
Rubio repeatedly said then-President Barack Obama "knows exactly what he's doing."
"There it is. There it is. The memorized 25-second speech. There it is, everybody," Christie said at one point.
Christie, who ran for president again in 2024 but dropped out before the first primary votes were cast, has said the moment took down Rubio's campaign -- which Rubio has significantly pushed back on.
2020 Democratic primary debates
McKinney said two moments from the most recent Democratic primary debates stand out, the first being when Sen. Elizabeth Warren took on Michael Bloomberg.
"I'd like to talk about who we're running against: a billionaire who calls women 'fat broads' and 'horse-faced lesbians,'" Warren said. "And no, I'm not talking about Donald Trump."
Warren said she didn't believe the Democratic Party should "substitute one arrogant billionaire for another."
Another highlight, McKinney said, was Kamala Harris' challenge to Joe Biden on the issue of segregation and busing. Harris challenged Biden on his past working relationship with two segregationist lawmakers.
"There was a little girl in California who was part of the second class to integrate her public schools, and she was bused to school every day, and that little girl was me," Harris said. "I will tell you that on this subject, it cannot be an intellectual debate among Democrats. We have to take it seriously. We have to act swiftly."
Biden-Trump general election debate
President Joe Biden and former President Donald Trump's debate ultimately changed the course of the 2024 election, after a poor performance by Biden exacerbated Democratic and voter concerns about his age and fitness to serve another four years.
Pressure after the debate for Biden to step down from the ballot intensified for weeks. He announced he was dropping out of the race 24 days later.
The showdown was held in June, making it the earliest general election presidential debate ever.
Biden's raspy voice, which he attributed to a cold, coupled with his inability to hit Trump on key Democratic issues stood out from the debate as Trump steered clear of some of his more bombastic claims.
Do debates change election outcomes?
Whether debate moments are game-changers in election outcomes has itself been, well, long-debated.
Experts said scholarship shows debates typically don't shift the outcome enough to make a big difference in terms of which candidate ultimately wins or loses the race.
"At best debates provide a nudge, like in close elections in 1960 and in 2000," Rottinghaus said. "All of those moments were very punctuated and had close elections and ultimately, the debates had a slightly larger role than traditionally they would have."
The outsized effect the debate played in Biden's campaign is something of an outlier, experts said.
"There are these moments where debates really do matter and can change the course of a race, but it rarely happens," said Rottinghaus.
Thompson said there are two strong indications in social scientific data about presidential debates, the first being that voters learn from them and the second being that the educational and preference effects of primary debates are much higher than those of general election debates.
"The primary primary debates do have a big impact because people are less settled in their opinion on candidates and at the same time partisanship is playing less of a role," Thompson said.
Thompson also noted that primary debates are consequential in that they tend to have a "winnowing effect" on the field of presidential hopefuls.
"People will leave the race because of poor performance, or that poor performance leading to a reduction in their polling averages and donations to the campaign," he said.
