Is history about to repeat itself? With less than a week to go until Britain’s third general election in five years, the Conservatives have failed to confront any of the shortcomings that led to them losing their majority in 2017. Their manifesto offered nothing new in terms of policy for young people or remain voters – two key groups who voted overwhelmingly against the Conservatives in 2017. Boris Johnson’s campaign has instead focused on winning the support of leave voters, attempting to avoid making any new promises and relentlessly criticising Jeremy Corbyn.

At first glance, this strategy would appear to be working: in the fourth week of the election campaign, the Conservatives were 10 points ahead of Labour on average in the polls, and on a universal swing would have won a majority of 46 seats. But beneath the headline figures in the polls, the numbers tell a story that should leave the Conservatives deeply worried.

In 2017, there were three main factors that scuppered the Conservatives’ hopes of winning an overall majority: a surge in support for the Labour party in the polls; a massive increase in youth turnout and support for Labour among young people; and remain voters swinging their support behind Labour as the most viable alternative to the Conservatives. All of these things are now happening again.

Labour’s vote share in polls has dramatically increased over the past few weeks. Whereas the Conservatives have lagged behind their 2017 performance (averaging 43% in polls last week, compared to 46% in the fourth week of the 2017 campaign), Labour has surged in the polls. Having averaged just 23% in polls in the week of 21-27 October, Labour is now averaging 33%, an increase of 10 percentage points in just a few short weeks; this is the same level of support that Labour had in the fourth week of the 2017 campaign.

A major reason for this has been the party’s success in attracting the support of people who voted remain in 2016. In the week of 21-27 October, Labour was winning the support of just 34% of remainers on average; the Liberal Democrats, meanwhile, were averaging 33%. Last week, however, Labour was averaging 48% with remain voters (+14), while the Lib Dems were averaging just 23% (-10).

‘Jo Swinson’s Lib Dems are now averaging just 13% in polls – 20 points behind Labour.’ Photograph: Ken McKay/ITV/Rex/Shutterstock

Labour has also increased its support among leave voters by five points (rising from 11% to 16%), but its support among remain voters has been far more significant. Virtually all of its gains among remainers have come from the Liberal Democrats, who have completely collapsed; having averaged 21% of the vote in the week of 16-22 September (2 points behind Labour), Jo Swinson’s party is now averaging just 13% in polls – 20 points behind the Labour party.

As in 2017, turnout among young people – and youth support for Labour – is likely to grow. In 2017, between the date that parliament voted for an election (19 April) and the final date of being able to register to vote (22 May), 1.9 million people aged under 35 registered to vote; over the same time period in 2019, 2.7 million people younger than 35 registered to vote – a 40% increase. Among voters younger than 25, registration rose by an even greater margin, increasing from 993,321 in 2017 to 1.5 million in 2019 – an increase of 47%.

Meanwhile, polls – which find it notoriously difficult to predict turnout – suggest that young people have become more and more likely to vote as the campaign has continued. In the week of 21-27 October, polls suggested that just 38% of 18- to 24-year-olds were certain to vote; by the week of 25 November-1 December, this had risen to 59% (+21). Labour’s support among young people, meanwhile, has increased enormously: whereas in the week of 21-27 October, Labour’s support among young people was just 39%, last week it was 55% (+16). This has largely been at the expense of the Lib Dems (-5 points) and Greens (-9 points).

In short, the idea that this election is a foregone conclusion is as incorrect as it was in 2017. Labour has made significant gains in the polls over the past few weeks, and the events of 2017 are largely being repeated. The Corbyn surge, the “youthquake”, the collapse in support for minor parties and the enthusiasm among Labour supporters – all these things occurred in 2017, and have occurred again. A slight error in the polls – such as the kind that occurred in 2015, 2016 and 2017 – could see Corbyn enter No 10.

If the Conservatives win an overall majority on 12 December, they will become the first government to increase their seat total when seeking a fourth term in office since the 19th century. Such a phenomenal task would require them to expand their support beyond the overwhelmingly pro-leave voters that enabled the Conservatives to win 42% of the vote in 2017. There are no signs, so far, that they have done so.

• Ell Smith is the founder of Stats for Lefties, a blog and podcast that examines polls and elections