It's a big question.

Would I be "concerned" if Nigel Farage moved in next door? You know what I mean. It turns out a huge percentage of the racialist slurs perpetrated by election candidates stems from an unchecked influx of Ukip. Who needs it, over the garden fence? One of those honest appraisals is required.

Certain politicians are having difficulty with that. In the case of Mr Farage and his remarks on Romanian migrants, Ed Miliband condemns the words, but not the person uttering the words. Equally, David Cameron fights shy of conceding that many former Tories have switched to a party with a gift for attracting racists - or do we call them slurists? - and feel no inhibition in doing so.

Nick Clegg informs us, meanwhile, that "the mask" slipped from Mr Farage when the latter told a radio audience last Friday that anyone concerned over a (non-existent) flood of Romanians and their alleged criminal networks was quite right. The Liberal Democrats' leader stopped short, however, of putting a name to what lies behind the mask. Trepidation stalks the land.

Reasons are not hard to find. The main Westminster parties have taken the line of least resistance where Ukip and Mr Farage are concerned. It is deemed foolish, electorally, to point out that voters flocking to the banner of Little Britain are less animated by nefarious "Europe" than by foreigners who happen to be east Europeans. The parties would like to win those voters back. This is otherwise known as pandering.

Some semantic nonsense ensues. Ukip is not racist, supposedly, but has an unfortunate yet consistent talent for attracting "idiots" (Mr Farage's word) who are racists to their pink fingertips. The party leader is no racist - he is vehement on this - but has a tendency to say things his many enemies are delighted to construe as racist. Those lefty, politically-correct types on The Sun would be a case in point. They took Mr Farage's comments on Romanians to be "racism, pure and simple".

Listen to the Ukip leader, if you can, and you will hear such descriptions dismissed as outrageous. His party has gone so far as to take out a full-page advert in the Daily Telegraph to explain why picking on people who were not born here is actually a blow for equality. What more could anyone need? Those attracted to Ukip because (I paraphrase) it would put an end to foreigners coming over here and stealing our zero hours contracts have been misinformed.

Strangely, the old, reliable test of duckness is being overlooked where Mr Farage and his party are concerned. You know the one: if it swims, walks and quacks like a duck, what are the odds on it being a duck? A duck of the Ukip sort also has a neat way of muddying the waters. Add "sensible", "fair-minded" and "how-dare-you-call-me-racist": the pond is murky indeed. But those are still racist ducks, all in a row, quacking madly.

Xenophobia does not cover it. There are some who will vote Ukip tomorrow who would send the Xenos right back where they came from. "Populism" is another word that will not quite do. These days the Westminster parties are as populist and stern as you like on the subject of immigration. What they lack is a willingness to let an honest voter say what he or she really thinks about foreigners. Mr Farage, protesting all the while, is less fastidious.

Ukip is a racist party. Anyone who votes for Ukip is ignorant of the fact - implausible, but not impossible - comfortable with the fact, or eager to exult in the truth. Mr Farage refuses to have facts, as he knows them, "brushed under the carpet", but he dislikes that particular fact. Prejudice is a vote-winner. He did not get where he is today - all over the BBC, as a rule - by ignoring a simple truth. Margaret Thatcher's fantasy of a Britain "swamped" by incomers remains potent.

There was a hope, once upon a time, that these islands were beginning to grow out of antique hatreds. When I was a child the world was almost entirely white. Decade by decade, things changed, always for the better. The suffocating thought of a society built around the blustering myopia of a Farage seemed to recede, bit by bit. But here we are in the 21st century: racism is back, popular, and granted legitimacy at every turn.

Now things become tricky. The easy answer to Ukip would be to say it is duping the ignorant. In some cases, that is no doubt true. In terms of those who are likely to give Mr Farage a big win in the European elections, however, another truth applies. A large number are prepared to endorse a racist party for the sake of a "protest vote". They are comfortable, to put it no higher, with what Ukip has to offer.

How many? A YouGov poll of 1933 adults asked at the start of the month if the Government should "encourage immigrants and their families to leave Britain". The question asked specifically whether those so "encouraged" should include children born in this country. Among Ukip supporters, 51% answered in the affirmative. The other parties were given news of their own to ponder.

Of Tories, 32% liked the notion of encouraged expulsion. Labour voters came in at 22%; LibDems at 13%. Taken together, 26% of "GB adults" thought that clearing the country of families with children born, raised and legally entitled to all Britain has to offer was an attractive, fair idea. You can see why Mr Farage and his devotees might soldier on despite all those little embarrassments with forthright candidates uttering racist tosh.

Ukip does not poll too well in Scotland. This is no tragedy, whatever your affiliations. But the idea that this country lacks its survivors from the 1950s was true before the referendum argument threw up sophistical nonsense and will remain true on September 19. The chance to build a better society will begin, as it must, with the society we have got.

Nevertheless, we have the word of the Survation polling company to support the belief that Ukip's core agenda is not anathema to a big minority among Scots. We have the suggestion - if you do not quibble over the weighting of the sample - that SNP supporters in 2011 are more receptive to Mr Farage and his kind than voting habits would suggest. As an argument composed of headlines, it amounts to saying Scots are not immune to the appeal of racist politicians.

Elections, those authentic polls, tend to say otherwise, but such facts rarely deter a psephologist. Ukip is engaged on a programme near identical to that being pursued by the Front National in France: to remain respectable at all costs while holding on to the affections of people who despise foreigners. That's the game.

Among the French, it is usual to decry Marine Le Pen and the Front as frauds concealing their purpose. Our democratic parties are less bold. Mr Farage will have no truck with his cousins across the Channel, strangely. Perhaps they are just too foreign. Or perhaps it would give the game away.