just one month ago, hillary clinton had amassed a 9-point lead over donald trump in national polls and had an even bigger advantage in several swing states. her eventual victory seemed to many to be all but assured, and democrats were so confident of winning that a landslide victory even seemed like a possibility.









but it<u+2019>s all been downhill for clinton from there. starting in mid-august, her leads in both national and swing state polls began to gradually shrink. and the events of this past weekend seem to have made her margin narrow even further, as trump has been getting some of his best state polls of the entire general election campaign.









importantly, clinton still appears to be narrowly ahead both nationally and in enough states to win. but the recent trends have not been good for her, and make a remarkably dramatic contrast with where the race appeared to be last month.









so what<u+2019>s happened? why has this race gotten so close all of a sudden?









matt yglesias offers the big-picture point that clinton is simply quite unpopular. but that still leaves open the question of why things have changed so quickly. inconveniently, a month of a campaign is a complex thing, with many different events unfolding either concurrently or one after another, which makes it difficult to test a clean theory about what<u+2019>s made the difference.









some combination of all this is most likely responsible for the shift we<u+2019>ve seen, due to voters changing their minds and, perhaps, differences in poll response rates <u+2014> though it<u+2019>s unclear which of these factors is most important. what is clear is that a race democrats hoped would be a landslide is now looking more like a nail-biter.









in the weeks following the democratic convention in late july, trump<u+2019>s poll standing plummeted. this was probably partly because clinton got a convention bounce, but another factor was likely trump<u+2019>s high-profile attacks on the family of the late capt. humayun khan. the kahn controversy was heavily covered in the press and earned trump a new round of condemnations from high-profile republicans.









but around august 17, trump decided to make a change. he installed a new campaign team. he stopped doing constant tv interviews where he<u+2019>d end up putting his foot in his mouth. he started doing more traditional and message-driven campaign events, as the wall street journal<u+2019>s monica langley writes.









and perhaps most importantly, trump has managed to avoid embroiling himself in any major new, campaign-consuming controversies (well, until thursday<u+2019>s birther flap, which hasn<u+2019>t yet played out in the polls). of course, he is being graded on a curve here <u+2014> as matt yglesias writes, even uneventful trump interviews usually contain several untrue or offensive statements that would shock us if any other politician were involved.









trump still isn<u+2019>t doing as well as we would expect a generic republican nominee to be doing. vox<u+2019>s fundamentals-based elections forecast suggests that he should be winning 50.9 percent of the two-party vote, and he<u+2019>s currently 3 points behind that. still, trump has generally spent the past month hammering home his critique of clinton rather than being dogged with questions about one offensive statement or another. and that could be helping bring some reluctant republicans back into his camp.









there<u+2019>s also one other big thing that<u+2019>s changed for trump in this time period: he finally started spending money on swing state campaign ads. until mid-august, hillary clinton had been spending millions on the airwaves essentially unopposed in every key state, but now the trump campaign has been investing millions in ads as well.









now, these ads are only seen by swing state voters, so we wouldn<u+2019>t expect them to make a dent in national polls. and trump has improved nationally, so they<u+2019>re not at the heart of what<u+2019>s going on. still, they could be making a difference at the margins in his performance in the swing states that will decide the election.









as trump has been improving his operation, clinton has been dogged by a series of negative news stories that could be hurting her to some extent.









on september 2, the fbi released a report of its findings in its investigation into clinton<u+2019>s emails. there wasn<u+2019>t really much <u+201c>news<u+201d> here, but it quite understandably led to a new spate of news stories with <u+201c>clinton<u+201d> and <u+201c>fbi<u+201d> in the headlines. and considering that the last time clinton sank this badly in the polls was in the weeks after fbi director james comey first announced his findings in early july, it seems that when the topic is in the news, clinton<u+2019>s poll standing suffers.









over this same late august/early september time period, a series of negative-sounding stories about the clinton foundation also were published. most of these stories didn<u+2019>t seem to amount to very much if you read their details closely. but the very fact that a bunch of negative-sounding stories about clinton appeared in the news helps create an aura of <u+201c>corruption<u+201d> around her, particularly when trump dubs her <u+201c>crooked,<u+201d> regardless of the fine details. (most voters aren<u+2019>t retaining the fine details here.)









meanwhile, clinton kept a relatively light campaign schedule in august so she could focus on fundraising instead. the side effect, though, was that she didn<u+2019>t have the opportunity to <u+201c>counterprogram<u+201d> those negative news stories with positive events putting her message out there.









<u+201c>clinton<u+2019>s decision to lay low in august <u+2026> will be debated for years,<u+201d> politico<u+2019>s glenn thrush writes. <u+201c>if she wins, her summertime fundraising blitz, meant to unleash a torrent of anti-trump advertising at campaign<u+2019>s end, will be regarded as strategic genius; lose and her decision is up there with michael dukakis in the tank.<u+201d>









i find that to be a bit overheated and doubt this made that much of a difference, but, hey, when voters did see a lot of clinton and her message during the week of the democratic convention, they did seem to like them well enough.









so the race had already gotten a good deal closer since mid-august. but then, the events of this past weekend seem to hurt clinton even more <u+2014> though it<u+2019>s not clear which mattered most.









first was <u+201c>deplorables-gate.<u+201d> at a fundraiser last friday, clinton disparaged <u+201c>half<u+201d> of trump<u+2019>s supporters at a fundraiser as belonging in <u+201c>the basket of deplorables <u+2026> racist, sexist, homophobic, xenophobic, islamophobic, you name it.<u+201d> clinton soon gave a semi-apology, saying that <u+201c>half<u+201d> was too much but reiterating that trump does indeed have many racist supporters. meanwhile, the trump campaign and much of the media quickly portrayed her remarks as a devastating gaffe akin to mitt romney<u+2019>s <u+201c>47 percent<u+201d> comments from 2012.









afterward, things got worse for clinton, as she felt faint and had to leave a 9/11 commemoration event on sunday, was recorded nearly collapsing while being led into her car, and belatedly admitted that she had been diagnosed with pneumonia two days earlier. all this seemed to some to vindicate rumors trump and his allies had been trying to spread about clinton<u+2019>s health for some time, and made clinton appear less than fully forthright.









this is speculative, but, like brendan nyhan of the upshot, i suspect the health news is hurting clinton more than deplorables-gate. yes, the trump campaign has seized on her remark, but the clinton team probably has better data and they now seem eager to discuss the topic (after the candidate<u+2019>s initial semi-apology).









furthermore, the deplorables comment seems like the type of inside-baseball campaign story that ordinary voters won<u+2019>t really care about, whereas clinton<u+2019>s health is far more striking. search data also suggests that people are far, far more interested in clinton<u+2019>s health than in the <u+201c>deplorables<u+201d> controversy.









now, it<u+2019>s possible that this sudden swing in the polls is affected somewhat by differential non-response rates, a phenomenon vox<u+2019>s jeff stein wrote about earlier this year. that is to say, the news of clinton<u+2019>s illness may have made her supporters less enthusiastic about even answering polls, so they<u+2019>d naturally show up less often in the results even after demographic weighting.









similarly, trump supporters may have been disproportionately less likely to respond to polls back in early august, when trump was under fire for his attacks on the khan family. that could have made clinton<u+2019>s poll leads look artificially large then, and a change in clinton supporter response rates could be making the race look unusually tight now. as stein wrote, andrew gelman and alan abramowitz have compiled evidence showing that what looks like big poll swings can often be explained partly by this effect.









yet if clinton voters truly are feeling so unenthusiastic about the race that they won<u+2019>t answer phone polls, that in itself indicates a major underlying enthusiasm problem her campaign needs to solve. furthermore, finding creative reasons to dismiss poll results that may not fit with your preconceptions has generally been a bad idea this year, as trump<u+2019>s primary rise and brexit have both shown.









as for whether this is the harbinger of a new normal in the race, well, we don<u+2019>t really know, of course. there are still 53 more days until election day, and much can happen in that time. (everything mentioned above happened in just the past month!) clinton<u+2019>s health could get better or worse. trump could avoid more gaffes or start backsliding like he did with birtherism on thursday. the media could cover trump more harshly now that it seems more likely he could win. the debates could go well or disastrously for either candidate.









what is clear is that a race democrats briefly thought they had in the bag no longer looks like such a sure thing.
3 explanations for why donald trump is suddenly doing better in the polls
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