The Conservatives hold a 15-point lead over Labour just days before polling day, according to the last Opinium poll for the Observer before the election.

The Tories appear to have maxed out the number of pro-Leave voters who will support them. However, the poll suggests that Labour is not winning Remain voters over at the speed required to close the gap. Boris Johnson’s party is on 46% of the vote, while Labour remains on 31%. The Lib Dems remain on 13%.

The poll suggests that Labour is slowly reclaiming some of the Remain voters who drifted to the Lib Dems. However, the Conservatives have also managed to win back some of their pro-Remain voters.

Jeremy Corbyn does not appear to be changing perceptions of his leadership in the same way he did in the 2017 election. In terms of who voters see as the best prime minister, Johnson is up 1 point to 37%, while Jeremy Corbyn is up to 21%. Public satisfaction with Johnson has decreased 2 points since last week’s poll to 28%, although outright preference for Corbyn has stayed level at 29%.

Brexit remains the most important issue at the election, but health has increased in importance. In the first week, the most important issue deciding voting choice was Brexit (40%), with health in distant second on 18%. Although this has narrowed, with days to go Brexit (33%) retains a slight lead over health and the NHS (22%).

However, in other regards, perceptions of Corbyn are not significantly worse than at the last general election. Currently only 29% can imagine him as prime minister, while three in five (59%) cannot. At the same stage in the 2017 general election, a third (34%) could imagine him as prime minister, compared to 56% who could not.

Perceptions of the election campaign have been poor compared to the last general election. At this stage in 2017, two in five (40%) said the campaign had left them with a more positive perception of Corbyn, while a similar proportion (38%) had been left with a more negative opinion of Theresa May.

In this campaign, Johnson appears to have come off slightly better than Corbyn. Three in ten (29%) said the campaign had left them with a better perception of the prime minister, while 28% said it had left them with a more negative perception of Corbyn.

Adam Drummond, the head of political polling at Opinium, said: “The Conservatives achieved ‘crossover’ a few weeks ago, the point where their lead over Labour was finally larger than at the equivalent point in 2017, indicating that Labour’s sudden surge that year wasn’t happening this year.

“The slow progress Labour were making has stalled and voters’ assessment of the two campaigns gives an indication as to why. At this point in 2017, voters expected the Conservatives to win a majority but more said Labour’s campaign had been successful than the Conservatives’. Similarly, voters said they’d become more positive about Jeremy Corbyn and more negative about Theresa May throughout the campaign even though they wanted and expected May to win.

“The picture in 2019 is starkly negative. Views of Johnson and the Tory campaign are mixed but the Labour campaign is seen as a failure by 55% of voters, worse than the 49% saying this about Theresa May’s disastrous 2017 campaign. Heading into the final week, a recovery is not impossible but doing so would require a turnaround even more spectacular than the one Mr Corbyn achieved last time.”

Opinium polled 2,003 UK people online from 4-6 December.