NICOLA Sturgeon is expected to make her third campaign visit to Shetland this week as her party becomes increasingly hopeful it can take the Holyrood seat from the LibDems.

The SNP have run a high-profile campaign with major figures in the party descending on the islands over the last few weeks to support grassroots activists.

Keith Brown, the party’s depute leader, and John Swinney, the depute First Minister, have joined SNP members in recent days to knock doors along with MEPs Alyn Smith and Christian Allard. MSPs including Gillian Martin, Ruth Maguire and John Mason have also joined in.

Ian Blackford, the party’s Westminster leader, is due to visit Shetland tomorrow as rival parties prepare for a final push before polling day on August 29.

A win for the SNP would mark the party’s first parliamentary win there and would be a major humiliation to the new LibDem leader Jo Swinson, who made an early campaign visit to Shetland. Scottish LibDem leader Willie Rennie is due to return today.

The by election was sparked by the resignation in June of former Scottish LibDem leader Tavish Scott , who had held the seat since 1999.

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In the 2016 Holyrood election, the SNP polled just 23% of the vote, against a LibDem vote of 67%. In the 2014 independence referendum, only 36% voted Yes, and 63% No.

Speaking after his weekend, visit Swinney praised his party’s candidate, Tom Wills, a marine engineer in the renewables sector, who he said has injected fresh thinking and new ideas into the by-election campaign.

“Tom Wills has tireless drive and a real determination to deliver more for families in Shetland”, he said.

The SNP duo were pictured in Wills’ home island of Bressay taking part in a weekly Park Run event, before they continued to pound the streets speaking with local voters.

The National: SNP candidate for the Shetland by-election, Tom WillisSNP candidate for the Shetland by-election, Tom Willis

Swinney added: “Make no mistake, we’re the underdogs in this by-election. Shetland has been a Liberal stronghold for almost 70 years, but campaigns are a marathon not a sprint and I’m confident that Tom can go the distance. From day one, Tom has run a positive and upbeat campaign – he’s leading the other candidates by example by rolling up his sleeves to inject some fresh thinking into how everyday life could be improved for islanders.”

Blackford is due to visit the islands tomorrow and is scheduled to hold a public meeting in Lerwick for WASPI campaigners.

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Transport has been a central issue in the campaign and yesterday the LibDem candidate, councillor Beatrice Wishart, a caseworker for local MP Alistair Carmichael, said she was proud of her party’s stance.

“From the delivery of the air discount scheme to securing funding in the Scottish Government budget for internal ferry services and leading the campaign for cheaper ferry fares, I am proud of the Liberal Democrat record,” she said. Wills said his party had made transport more affordable and introduced 50% off family flights to Shetland, 20% off Northlink ferries, and provided £5 million for local inter-island ferries.

The constituency has been represented by Liberal politicians for nearly 70 years, including former Liberal UK leader Jo Grimond and former Scottish LidDem leader Jim Wallace.

John Curtice, professor of politics at Strathclyde University, told the Sunday Times: “It would be a remarkable upset if the Liberal Democrats were unable to retain the seat. The Northern Isles have been a Liberal stronghold ever since Jo Grimond first won the Westminster seat in 1950, and even at the height of their popularity in 2015 the SNP were unable to wrest the area away from its traditional loyalties.

He continued: “True, the Liberal Democrats can anticipate a tougher fight than usual ... But, equally, the by-election is being fought against the backdrop of a revival in the Liberal Democrats’ electoral fortunes in the wake of the Brexit impasse that should help the party.”