The SNP is expected to win back seats from both the Conservatives and Labour

Jeremy Corbyn launched the final day of Labour’s election campaign before dawn on the banks of the Clyde, with party activists and their children framed by the lights of a Christmas tree.

Standing on the border of Nicola Sturgeon’s Glasgow Southside constituency, Corbyn brought loud cheers from Labour candidates and campaigners by declaring: “The only way of getting rid of a Tory government is by voting Labour all across the country, including here in Glasgow and all across Scotland.”

It was a provocative claim and a provocative place to stand: Labour had arranged Corbyn’s rally in a contituency it believes it can steal from the Scottish National party, Glasgow South West.

Alerted by tweets from journalists covering his speech, Sturgeon retorted on Twitter: “There’s not a single Tory/Labour marginal in Scotland. Only the SNP can beat the Tories in Scotland. Voting Labour will help the Tories.”

An hour later, Sturgeon began the SNP’s final push by helping sort broccoli and brussels sprouts in a greengrocer cooperative in Labour’s safest Scottish seat, Edinburgh South, where she repeated that message. “The SNP is the main challenger to the Tories,” she said. “Voting for other parties risks helping the Tories.”

The spat between Sturgeon and Corbyn illuminated the complex electoral picture in Scotland. A significant number of the country’s 59 Westminster seats are marginals, and four are in the top 10 most marginal seats in the UK.

Despite Sturgeon’s claim that there are no Tory-Labour marginals, there is less than a percentage point between the SNP, the Conservatives and Labour in the SNP’s seat of Lanark and Hamilton East. All three parties claim they could win there.

Yet Sturgeon has won over much of Labour’s support in Scotland and is expected to win back a handful of seats that Labour took in 2017. The SNP is the closest challenger in every one of Labour’s seven Scottish constituencies.

Facebook Twitter Pinterest The SNP leader, Nicola Sturgeon, during a visit to a community greengrocer in Edinburgh on Wednesday. Photograph: Jane Barlow/PA

A number of seats could change hands on Thursday, but fewer than was suggested by polls at the start of the campaign. A YouGov poll released on Tuesday evening indicated that the SNP could regain six of the 21 seats it lost in 2017, taking back seats from both the Conservatives and Labour.

YouGov predicts that the Tories will save nine of the 13 seats it is defending, and Labour – despite a run of dire polls during this campaign, will retain five of its seven. That would surprise other Scottish party strategists. Although Labour has recovered since a YouGov poll in October put its vote at a historic low of 12% (Panelbase put it recently at 21%), few believe it will hold more than three seats.

YouGov predicts that the Liberal Democrats, deflated by a poor campaign, will win four seats – the same number it won in 2017.

Tory strategists suspect there will be a few shocks. They believe the Lib Dems will win back the UK’s most marginal seat, Fife North East, held by the SNP’s Stephen Gethins in 2017 by two votes. YouGov predicts Gethins will retain it. The Conservatives say thousands of Tory voters, including their own activists, will vote Lib Dem tactically to oust the SNP.

The Tories are expected to lose several seats to the SNP, including Aberdeen South – suddenly vacated by the former MP Ross Thomson early in the campaign after Labour’s Paul Sweeney accused him of sexual assault in a Commons bar – and also Ochil and South Perthshire.

They are also resigned to defeat in Stirling, where Alyn Smith, an MEP who became the poster boy for the SNP’s anti-Brexit campaign in Brussels, has built a strong pro-remain coalition in a seat that voted 67% in favour of staying in the EU in 2016.

The Tories say this election has come down to four interlinked issues in Scotland: “Independence, Nicola, Brexit and Boris.” Boris Johnson’s reputation has proven toxic for the Conservatives in some seats, while the Tories’ relentless focus on Sturgeon and her early attempts to make independence a defining issue of this election appear to have had some impact. A YouGov poll for the Times on Saturday said support for independence had dropped five points to 44% since September.

Labour insists the national polls have underplayed the strength of its local campaigns; its strategists believe YouGov’s final forecast is closer to the actual picture. Labour chose to launch Corbyn’s last day of campaigning in Glasgow South West because it believes its candidate, Matt Kerr, could win.

Much depends on turnout, and some results will be nail-bitingly tight. “We are very much in the game,” said one Labour official. “We think he has a good chance of winning.”

SNP strategists say their marked shift in the final days to attacking Johnson and the Tories reflects the anxiety they are picking up from voters about the prospect of another five years of a Johnson premiership. Their biggest concern now is voter complacency on polling day, which so significantly affected their results in 2017.

“We have more people out campaigning than ever before,” said one official. “Last time they thought: what’s the point if we’re not pushing for a second independence referendum? But now when the Tories attack, we have something to say.”