从本质上讲，政治分析中一个不变的说法是，什么都不重要。有时，人们会觉得即使是一次重大的失态或丑闻也不能影响选民对候选人的看法，即使是重大新闻事件也不能改变公众对问题的看法。
但有时候，事情确实很重要。总统辩论是命中注定的事。上周副总统卡玛拉·哈里斯和前总统唐纳德·特朗普之间的辩论产生了比选民想要的更少的政策细节，但哈里斯一路上成功地将特朗普描绘成一个坏形象。在辩论后的一周里，民调显示民主党候选人的支持率略有上升。因此，根据538的预测模型，在9月16日星期一，哈里斯赢得选举的机会达到百分之六十一——超过了她8月26日的前一个高点。
如果我们看看所有完全在辩论后进行的民意调查，并将它们与每个公司的辩论前调查进行比较，哈里斯在大多数调查中都取得了小幅进展。根据一项调查，哈里斯公司的利润率上升了1个百分点益普索/路透社上周晚些时候公布的全国民意调查;2分在RMG研究公司的投票;2分根据晨间咨询;2分根据大村庄;和1分根据社会策略。唯一的例外是莱格,雷德菲尔德&威尔顿策略和益普索/美国广播公司新闻辩论后的民意调查显示，与他们上次的调查相比，哈里斯分别失去了1个百分点，原地踏步和原地踏步。
538的全国和各州民意调查的平均值一致认为，哈里斯自辩论以来取得了边际收益。截至东部时间9月17日星期二上午9点，哈里斯在全国民调中平均领先特朗普2.9个百分点比她在辩论日领先的2.5个百分点略有上升。这0.4个点的增益比辩论后的平均变化在1952年的选举民意调查中——但话说回来，随着两极分化，大多数观点的变化现在都变小了。值得注意的是，哈里斯在全国民调中仍比8月底的高点低了约1个百分点。
在全国民调中，对哈里斯来说，真正的好处不是她获得了0.4%的支持率;那就是她已经阻止了特朗普的收益。上周之前，自8月下旬以来，特朗普在哈里斯的全国普选中获得了约半个百分点的优势。如果他继续沿着这条路走下去，他将有望在本月晚些时候赢得538预测的比赛——也许就在本周。相反，哈里斯适度地提高了她赢得比赛的机会。
但是因为总统选举是由选举团决定的，所以真正重要的是州民调，而不是全国民调。除了我们已经提到的全国民调，州民调也显示哈里斯获得了实实在在的好处。在新罕布什尔州，圣安瑟姆学院调查中心的一项民意调查发现，哈里斯比特朗普高出8个百分点。好了2分高于哈里斯辩论前的平均水平在这个州。民意调查阿拉斯加,阿肯色州和新墨西哥州也高于平均水平。来自右翼的民意调查特拉法尔加集团周一公布的数据显示哈里斯在内华达州领先2个百分点。民意测验来自内在优势和高度评价马凯特大学法学院发现哈里斯在威斯康星州的潜在选民中分别上升了2和5个百分点。周日，一直备受关注的塞尔策公司/得梅因登记民意调查显示特朗普在爱荷华州仅领先哈里斯4个百分点，我们的模型曾预计特朗普会以8个百分点的优势获胜。
是的，非摇摆州的转变很重要，即使哈里斯最终不太可能获胜。民调走势通常与各州相关，这意味着如果哈里斯在爱荷华州和阿肯色州获得胜利——更不用说全国范围了——她很可能在宾夕法尼亚州和北卡罗来纳州也获得胜利。
所有这些都导致了我们的选举预测向哈里斯相当大的转变(这可能是更有侵略性比我们的民意测验平均值对民意测验中的相关运动的反应更大)。我们的模型对七大摇摆州的两名候选人之间的最终差距的预测是，哈里斯今天比上周高出约1个百分点。我们在威斯康星州的预测从哈里斯+2变成了哈里斯+3;在密歇根州，从哈里斯+1.5到哈里斯+2.2;在宾夕法尼亚州和内华达州，从哈里斯+0.1到哈里斯+1.5;而在乔治亚州、北卡罗来纳州和亚利桑那州，从特朗普+1到哈里斯+0.2。
事实上，民意调查对哈里斯来说是如此(相对)有利，以至于该模型实际上预测了一次比当前全国民意调查平均水平更民主的全国普选。我们的模型根据每个州的估计投票率计算出隐含的全国民众投票，如今这个数字更接近哈里斯+4.2，而不是哈里斯在全国民调中的2.9个百分点的领先优势。这与2012年的情况类似，当时州民调显示巴拉克·奥巴马总统比全国民调更胜一筹(奥巴马最终击败了共和党提名人米特·罗姆尼的全国民调平均值)经过超过3分).
全国民意调查中的全国选民与州民意调查中的选民之间的差异听起来可能很小，但事实上1.5个百分点可能最终决定整个选举。哈里斯和特朗普之间的预测差距目前在亚利桑那州、乔治亚州、内华达州、北卡罗来纳州和宾夕法尼亚州等于或小于1.5个百分点，这一集团加起来相当于68张选举人票。
在2020年的大选中，现任总统乔·拜登最终需要赢得至少3.8个百分点的全国普选(假设全国统一摇摆)，才能赢得足够多的州来赢得270张选举人票。今年，由于她在州民调中的地位强于全国民调，我们的预测认为哈里斯只需要赢得全国普选的2.1个百分点就有望获胜。然而，这仍然意味着选举团可能会帮助特朗普，这意味着哈里斯必须保持她目前在北方战场州的领先优势。这就是为什么我们的预测给哈里斯61/100的获胜机会，而不是72/100(她目前赢得全国普选的机会)。
不过，归根结底，现在还为时尚早:离选举日还有七周时间，许多大公司还没有公布任何辩论后的数据。我们将不得不继续关注数据，看看哈里斯和特朗普的机会如何变化。历史已经证明，竞选活动可以挖掘新信息，强化对候选人的看法，或者剥夺失败者改变竞选的最后机会。在竞争激烈的全国选举中，这一点比以往任何时候都更加真实，尽管两极分化程度更高。538的投票平均数和选举预测模型将继续更新最新的民意调查。
Polls show Harris gaining after the presidential debate
A constant refrain in political analysis is, essentially, that nothing matters. Sometimes, it can feel like not even a massive gaffe or scandal can affect how voters feel about a candidate, and not even major news events can move public opinion on issues.
But sometimes, things do matter. Presidential debates areone of those things. Last week's debate between Vice President Kamala Harris and former President Donald Trump producedfewer policy specifics than voters wanted, but along the way Harrissucceeded in painting Trump in a bad light. In the week since the debate, polls have shown a slight increase in support for the Democratic nominee. As a result, on Monday, Sept. 16, Harris's chance of winning the election according to 538's forecasting modelreached 61-in-100— surpassing her previous high from Aug. 26.
If we look at all the polls that have been conducted entirely after the debate and compare them with each firm's pre-debate survey, Harris has made small gains in most of them. Harris gained 1 percentage point on margin according to anIpsos/Reutersnational poll released late last week; 2 points inRMG Research'spolling; 2 points according toMorning Consult; 2 points according toBig Village; and 1 point according toSoCal Strategies. The only exceptions areLeger,Redfield& Wilton StrategiesandIpsos/ABC News, whose post-debate polls showed Harris losing 1 point, standing pat and standing pat, respectively, compared with their last surveys.
538's averages of national and state polls agree that Harris has made marginal gains since the debate. As of 9 a.m. Eastern on Tuesday, Sept. 17,Harris leads Trump by an average of 2.9 points in national polls, up ever so slightly from her 2.5-point lead on debate day. That 0.4-point gain is considerably smaller than theaverage post-debate changein election polls going back to 1952 — but then again, with polarization, most changes in opinion are smaller now. Notably, Harris is still down about 1 point from her late-August high in national polls.
In national polls, the real boon for Harris is not that she has gained four-tenths of a percent of support; it's that she has put a stop toTrump'sgains. Before last week, Trump was gaining about half a point of popular-vote margin nationally on Harris since late August. If he had continued on that path, he would have been favored to win the race in 538's forecast by later this month — perhaps as soon as this week. Instead, Harris is the one who has modestly improved her chances of winning the race.
But because presidential elections are decided by the Electoral College, it's the state polls, not national polls, that really matter. And in addition to the national polls we've already mentioned, state polls also show real gains for Harris. In New Hampshire, a poll from Saint Anselm College Survey Center found Harris up by 8 points over Trump,2 points betterthan Harris's pre-debate averagein the state. Polls inAlaska,ArkansasandNew Mexicoalso came in above average. A poll from the right-leaningTrafalgar Groupreleased Monday showed Harris up by 2 points in Nevada. Polls fromInsiderAdvantageand thehighly ratedMarquette University Law Schoolfound Harris up by 2 and 5 points, respectively, among likely voters in Wisconsin. And on Sunday, the always-closely-watchedSelzer& Co./Des Moines Register pollshowed Trump leading Harris by just 4 points in Iowa, a state our model had been expecting Trump to win by 8.
And yes, shifts in non-swing states matter, even if Harris is unlikely to win them in the end. Polling movement is often correlated from state to state, meaning that if Harris is gaining in Iowa and Arkansas — not to mention nationally — she's probably also gaining in Pennsylvania and North Carolina.
All of this nets out to a pretty sizable shift toward Harris in our election forecast (which can bea bit more aggressivethan our polling averages in reacting to correlated movement in polls). Our model's predictions for the final margin between the two candidates in the big seven swing states are about 1 point better for Harris today than they were last week. Our forecast in Wisconsin has gone from Harris+2 to Harris+3; in Michigan, from Harris+1.5 to Harris+2.2; in Pennsylvania and Nevada, from Harris+0.1 to Harris+1.5; and in Georgia, North Carolina and Arizona, from Trump+1 to Harris +0.2.
In fact, the polls are so (comparatively) good for Harris that the model is actually forecasting a national popular vote that is more Democratic than the current national polling average. Our model calculates an implied national popular vote based on estimated turnout in each state, and today that number is closer to Harris+4.2 than Harris's 2.9-point lead in national polls. This echoes 2012, when state polls looked better for President Barack Obama than national polls did (Obama ended up beating his national polling average over Republican nominee Mitt Romneybymore than 3 points).
This difference between the national electorate in the national polls and the one implied by state polls may sound small, but in fact 1.5 points could end up deciding the whole election. The forecasted margin between Harris and Trump is currently equal to or smaller than 1.5 points in Arizona, Georgia, Nevada, North Carolina and Pennsylvania — a bloc that is together worth 68 electoral votes.
In the 2020 election, now-President Joe Biden ended up needing to win the national popular vote by at least 3.8 points (assuming a uniform national swing) in order to carry enough states to win 270 electoral votes. This year, thanks to her stronger standing in state polls than in national ones, our forecast thinks Harris needs to win the national popular vote by only about 2.1 points in order to be favored to win. However, that still means the Electoral College will probably help Trump, meaning that it's essential for Harris to maintain her current lead in the northern battleground states especially. That's why our forecast gives Harris a 61-in-100 chance of winning instead of 72-in-100 (her current chances of winning the national popular vote).
Ultimately, though, it is still early days: We have seven weeks left until Election Day, and many major firms have yet to release any post-debate data. We will have to keep watching the data to see how Harris's and Trump's chances change. As history has shown, campaign events can unearth new information, reinforce perceptions of candidates, or deprive underdogs of a last chance to shake up the campaign. That's truer than ever in tightly contested national elections, regardless of higher levels of polarization. 538'spolling averagesandelection forecasting modelwill continue to update with the latest polls as they are released.
