A barely concealed anxiety has taken hold in the Scottish Conservative party. Its striking resurgence under the leadership of Ruth Davidson is at risk of coming to a sudden, painful halt this week at the hands of Nigel Farage.

A spate of opinion polls suggest the Scottish Tories could lose their sole MEP, Nosheena Mobarik, in the European elections on Thursday, with voters defecting en masse to Farage’s Brexit party.

“I’m not focusing on the polls at all,” said Mobarik, a softly spoken businesswoman who became one of Scotland’s six MEPs midway through the current European parliament. “I just say to people that the Conservative party is the only one which will ultimately deliver on Brexit, so stick with us.”

She may not study the polls but her advisers do, and so does Davidson. Tory support has plummeted and Brexit party support has jumped. A Panelbase poll for the Sunday Times put the Tories on 11% and Farage’s outfit on 16%. A poll released on Sunday by YouGov and Datapraxis for Hope not Hate and Best for Britain put the Tories on 10% and the Brexit party on 20% in Scotland. The figures suggest Mobarik could well lose her seat.

The Scottish Tories fear defeat on Thursday could be the start of something far worse than a brief protest vote. If Farage triumphs across the UK, it would have a big impact on the Tory leadership battle in Westminster, and thus the fate of the Brexit negotiations and, in turn, Scottish support for independence.

Facebook Twitter Pinterest Farage at a Brexit party rally in Edinburgh on Friday. Photograph: Jeff J Mitchell/Getty Images

There is a painful irony in this for Davidson: the Tories’ renaissance in Scotland was built in large part by her successful exploitation of public anger at Nicola Sturgeon’s attempts to convert the Brexit vote in 2016 into a justification for independence.

In the general election of June 2017, the Tories won a swathe of SNP seats, particularly in the rural north-east where the former first minister Alex Salmond and the SNP’s Westminster leader, Angus Robertson, were deposed. Suddenly the Scottish Conservatives went from holding one Westminster seat to 13.

That trend is now in reverse. The SNP are on course to win three of Scotland’s six European seats, chiefly at the expense of Labour, after emphatically embracing the remain cause. But a million Scots voted for Brexit and many are swinging firmly behind Farage. Their anger at the UK government’s failure to deliver was palpable at his rally in Edinburgh last Friday.

The Brexit party’s lead candidate in Scotland, Louis Stedman-Bryce, who is black and gay, believes he exemplifies the broad appeal of their cause to leave voters. Many among the 400 crowded into the Corn Exchange were arch-Brexiters, but some voted yes to independence and others were Labour leave voters. They all felt Farage represented them.

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“It’s not easy being a Brexit supporter, is it?” Stedman-Bryce asked the crowd. “The SNP would have you believe that Scotland voted almost unanimously to remain in the EU. We know that’s not true, don’t we? There are over 1 million Scots in the country who voted to leave the EU. [I] voted with you guys and we have been forgotten.”

Mary Turnbull, 71, had travelled from Irvine, on the west coast of Scotland, with her husband, Ian, to attend the rally. “We hadn’t been represented by anyone until Nigel Farage came back,” the couple said. “Theresa May has broken every promise she made to us.”

The independence question gives the battle to succeed Theresa May even greater significance for the Scottish wing of the Conservative party. It is widely felt that Boris Johnson would be a disaster: the embodiment of English Tory elitism, his brand of brash Brexiter politics is seen as toxic to Scottish voters.

Sturgeon has seized on that mood, suggesting on the BBC’s Andrew Marr Show on Sunday that a Johnson premiership could be sufficient grounds for a second independence referendum. “The last thing I should be doing is narrowing Scotland’s options,” she told Marr. Davidson has instructed her party’s MPs and MEPs to stop any anti-Johnson rhetoric to avoid fuelling Sturgeon’s strategy.

Facebook Twitter Pinterest Scottish Tories are said to be concerned about the possibility of Boris Johnson taking over the UK party. Photograph: Andrew Yates/Reuters

Most Scottish Tory parliamentarians want Michael Gove as party leader, though some support Johnson. What they fear more is the possibility of the former Brexit secretary Dominic Raab winning. In private, they say Johnson is malleable and pragmatic, but they see Raab as an ideologically rigid and fundamentalist rightwinger who has ignored their advice on Scottish affairs.

At an STV hustings on Monday night, Mobarik was pressed by other parties’ European candidates for her views on Johnson’s suitability. She dodged their questions but told the Guardian the Tories need a unifying figure at the helm. She is a fan of the one nation Toryism once espoused by David Cameron and still championed by Davidson and David Mundell, the Scottish secretary.

Q&A How do European parliamentary elections work in the UK? Show Hide The UK elects 73 members (MEPs) to the European parliament, which is made up of 751 MEPs elected by the 28 member states of the EU. The UK is split into 12 European electoral regions, and each region is represented by between three and 10 MEPs. The constituencies are:

South East England (10 MEPs)

London (8)

North West England (8)

East of England (7)

West Midlands (7)

South West England (including Gibraltar) (6)

Yorkshire and the Humber (6)

Scotland (6)

East Midlands (5)

Wales (4)

North East England (3)

Northern Ireland (3) You can find out who is standing for election in your area here. In England, Scotland and Wales, voters can choose to vote for one party or individual. The ballot paper lists the parties standing with the names of their potential MEPs, as well as any individuals who are standing as independent candidates. The D’Hondt method of proportional representation is used to calculate how many seats each party or individual receives. In Northern Ireland, the single transferable vote method is used, where each voter ranks candidates in order of preference, marking 1 beside their most preferred candidate, 2 beside their second choice, and so on. These votes are then used to allocate Northern Ireland’s three MEPs. Those elected as MEPs on 23 May will represent the UK when the new European parliament assembles on 1 July, until such time as the UK ceases to be a member of the European Union.

“When people are given a leadership position, they know they have to lead the whole country, they have to bring people together,” Mobarik said. “Then the pragmatism kicks in – that’s if they’re not of a very extreme nature.”

A former chair of the business group CBI Scotland, she believes the Tories would make a fundamental mistake if they tacked further to the right to head off the Brexit party’s challenge after this week’s election. She fears Farage’s new MEPs will be a disruptive, antagonistic force in the European parliament, when diplomacy will be needed.

“We’ve got to keep fighting for the middle ground. I keep on saying in the European parliament there are extremes on both the left and the right, and it’s quite concerning, to be honest.”