After attracting less than 1% of the vote in the 2010 Holyrood election and never having managed to retain a deposit in a Scottish election, could the European elections on May 22 mark Ukip's breakthrough in Scotland?

Nigel Farage apparently believes so. The Ukip leader has predicted to The Herald that his party will win one of Scotland's six European Parliament seats, shaking up the referendum debate and boosting the No campaign in the process.

No politician would ever be caught on the pre-election hustings predicting anything other than resounding victory, so only an analysis of the polls can shed light on the true likelihood of a Ukip win. Five Scottish polls since January have seen Ukip's share of the vote rise, but the party is still bumping along at 10% (one aberrant 18% score on a tiny sample notwithstanding), which is a long way from a guarantee of a seat. Even if Ukip did win one, it is hard to see how this would boost the No campaign.

Scotland's inherent tolerance and liberalism are frequently overstated, but it is true to say that Mr Farage is perceived by many as a disreputable troublemaker whose relentless anti-immigration message breeds division and risks intra-communal hostility; not exactly a boon to the pro-UK campaign. Obsessed as he is by the notion the EU has stolen British sovereignty, he imagines a win for his party will show his views are widely shared north of the Border and would expose the notion of Scottish "independence" within the EU as a sham. But fervent Euroscepticism has always been a niche interest among Scots. The more likely explanation for Ukip's small recent surge of support here is that it has, for now, appeal as an anti-establishment party of protest for voters who feel disillusioned by the mainstream parties.

That is not to say Scots are wholesale supporters of the EU. Two polls earlier this year on whether an independent Scotland should be in or out of the EU put support for leaving at almost one-third. Even so, neither Britain's membership of the EU, nor immigration control (Ukip's other big ticket policy) are defining issues for voters in Scotland as they are in many parts of England.

There are many reasons to be wary of Ukip. Its latest hysterical anti-immigration poster campaign ("26 million people are looking for your job") fell on the wrong side of provocative and a number of Ukip supporters have revealed themselves to be racist, Islamophobic and homophobic, even if Mr Farage insists the party is not. But, in a democracy, the Ukip leader still has a right to say his piece. Last year during a visit to Edinburgh, he ended up barricaded in a pub while an angry crowd, led by pro-independence supporters, jeered at him to "Go back to England".

Ironically, that handed Mr Farage the perfect excuse to accuse the mob of racism in the form of anti-Englishness. More protesters are expected today when Mr Farage returns to the capital. They have every right to demonstrate, but another show of intolerance will do their cause no favours. Let Mr Farage speak. Then voters can decide what they think of him.