Harris regains small poll lead post-debate as US election inches closer

Kamala Harris has re-established a crucial polling advantage over Donald Trump following this week’s debate, which a clear majority of voters believe she won , according to a range of surveys.

The latest Guardian polling trends tracker shows the US vice-president regaining a small lead over the Republican nominee since Tuesday’s encounter in Philadelphia, a shift from surveys at the start of the week when the pair were essentially tied.

The movement is supported by individual polls, some of which show Harris with a bigger lead than the 0.9% advantage displayed in the Guardian tracker.

A Reuters/Ipsos poll , the first to be conducted since the debate, had Harris ahead by five points, 47 to 42%, a 1-point rise on the lead recorded in the week after last month’s Democratic national convention.

Related: Scoffs, smiles, squints: how Kamala Harris’s face spoke volumes in Trump debate

A separate Morning Consult survey published on Thursday showed a similar lead, 50 to 45%, up from the three- to four-point advantage Harris was registering before the debate. Tellingly, the poll reflected a loss of support for Trump, perhaps supporting some pollsters’ argument that his erratic performance in Tuesday’s encounter – which was watched by 67.1 million viewers – damaged his credibility.

Two other polls by YouGov and Leger give Harris a four- and three-point lead respectively. Generally, the post-debate polls present a rosier outlook for the vice-president than surveys beforehand, which suggested that the surge in popularity she experienced after replacing Joe Biden as the Democrats’ nominee had stalled, allowing Trump to draw close to even in national polls, and even edge ahead in one New York Times/Siena survey.

All available indicators suggest that the turnaround has been triggered by the events of the debate, where Harris was broadly seen as cutting a calm, controlled figure while getting under the skin of Trump – who repeatedly veered off policy message to go on wild tangents about immigrants and crowd sizes at his rallies.

While so far declining Harris’s challenge of a second debate , the former president nevertheless claims that he won the exchange .

Survey respondents beg to differ. The Reuters/Ipsos polls showed 53% who had heard something about the encounter believed that Harris had come out on top, as opposed to 24% thinking Trump had prevailed. The Morning Consult poll showed a similar margin, 55-25%, in favour of thinking Harris had won.

That is broadly in line with three earlier post-debate polls – conducted by CNN, YouGov and CNN – which gave Harris an average debate-winning margin of 23%.

“She definitely got a bump – and if those polls are accurate, a little more of a bump than I thought,” said John Zogby, a veteran pollster who believes key moments in some debates had small but decisive impacts on the outcomes of past presidential elections.

“Clearly Kamala Harris won the debate. There are enough polls out to show that and other observers beyond the polls also believe that she won. I think, more importantly, Trump lost the debate. He lost a lot of credibility, in addition to having lost the debate.”

The burning question, however, is whether one lost debate translates into a lost election.

Frank Luntz, a Republican pollster and strategist who forecast in advance of the debate that its winner would prevail in November, suggested that the sour nature of Trump’s showing had sealed his electoral fate.

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“It was a pretty negative performance. Pretty pessimistic, cynical, contemptuous and I think that this will cost him, yes,” he told the interviewer Piers Morgan. “I think that he loses because of this debate performance.”

Although eight weeks separate Tuesday’s debate from election day on 5 November, the wafer-thin polling margins – particularly in key battleground states – mean the ripples emanating from Trump’s multiple miscues are likely to have an outsize effect, Luntz argued.

“There are very few undecided voters left,” he said. “It’s about 5% of the vote – and they only matter in seven states. And those states are too close to call. So essentially we are looking at less than 1% of America. But they heard nothing from Trump to give them a sense of anything that would be different going forward.”

Zogby, by contrast, said it was “too early to tell” the debate’s electoral impact and identified weaknesses in Harris’s performance that may return to haunt her.

“She lost some points on substance,” he said. “Right from the very beginning [when she was asked] can you tell the American people that they’re better off than they were three and a half years ago … she jumped right into the future. That’s going to dog her because three-quarters of the US voters think the country is headed in the wrong direction – and the blame goes to the party on top and the president on top. She owns the administration’s successes, but she also owns inflation and the economy.

“So I will say advantage to her on presentation and being cool, but there was no knockout blow.”

One additional piece of fallout from Tuesday’s debate might tilt the balance in Harris’s direction – the intervention of Taylor Swift.

The singer endorsed Harris immediately after the event, a move that prompted about 400,000 people to visit a voter registration link she posted on her Instagram, which has 284 million followers.

Related: Taylor Swift has endorsed Kamala Harris. Donald Trump has only himself to blame

A late young voter registration surge favouring the Democrats could significantly affect the electoral role played by the age 18-29 voter demographic, among which Harris’s current 15% lead over Trump compares unfavourably with the 28% advantage Biden held in his 2020 election victory.

In a segment on CNN, Harry Enten, the network’s polling specialist, illustrated a trend towards Republican registration among voters under 30 in battleground states that are key to winning the White House.

In Pennsylvania and North Carolina, two fiercely contested swing states, the GOP had drastically whittled back the Democrats’ lead among young voters of four years ago, thanks to a superior registration drive, he said, the effect of which Harris could only hope Swift’s endorsement could reverse.

“Kamala Harris will absolutely welcome in the support of Taylor Swift if she can move young voters at all,” Enten said. “The bottom line is [Harris] is not doing as well among young voters as you might expect the Democrat to necessarily be doing, based upon history.”

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