Charlie loves Zac Goldsmith, and showed his affection by licking the candidate’s face. But Charlie is a Cocker Spaniel, so will not have a vote in the London Mayoral elections in two days’ time.

Goldsmith’s chances as the Conservative candidate in that contest are not especially good. In last year’s general election, Labour won 1.55 million votes in London to the Tories’ 1.23 million, and the opinion polls still put the Labour candidate, Sadiq Khan, well ahead.

After spending some time yesterday with Goldsmith and his campaigners, I cannot claim to have picked up any clear signs of a change in the Conservatives’ favour, of the kind that became perceptible in West Yorkshire during the general election.

The political weather in London has become stormy. Harsh accusations are hurled to and fro: Goldsmith condemns his opponent, Sadiq Khan, for having shared a platform with extremists, while Khan’s people say Goldsmith is a racist, who wants to make it impossible for any Muslim, no matter how moderate, to become Mayor.

But no one knows what effect these accusations will have on the voters. Nor is it clear whether the anti-semitism row which is convulsing Labour will reduce Khan’s vote.

Will Labour supporters refuse to turn out? That, allied to a strong turn-out by his own sympathisers, is Goldsmith’s best hope.

Some Tories think he is still in with a good chance. An activist who had cleaned up during the general election by betting, in defiance of pundits and pollsters, on a Conservative overall majority, told me she has placed the same bet, at odds of seven to one, on Goldsmith winning the mayoral election.

But among the several dozen Tory activists who were waiting yesterday morning outside Wimbledon Station to greet Goldsmith, the most common emotion was one of good-humoured uncertainty about the outcome.

They like Goldsmith, and he is good at showing his appreciation of them. When he arrived yesterday morning in Wimbledon, he began by saying:

“Thank you so much. You’re absolutely heroic. It’s a bank holiday. You could have been frolicking in Richmond Park.”

Here is a Tory who admits the role that pleasure – the frolic – plays in life. A considerable number of people, both from the general public and from the Tory group, wanted to have selfies taken with him, and this he agreed to with unwearying good humour.

But his candidacy has become, in its final days, less pleasurable. For he finds himself asked again and again about his attacks on Khan.

An interviewer and a camera team from BBC London were waiting to question him about his onslaught on Khan in the Mail on Sunday, illustrated by a picture of a bus wrecked by a suicide bomber in the 2005 terror attacks on London.

Goldsmith said “I stand by every word in the article”, but admitted it was “an odd choice of picture”. He added that “any half-intelligent person knows when you write an article in the papers you don’t choose the picture”.

Immediately after this interview, a woman of Indian descent approached Goldsmith and told him: “I regard your campaign as really divisive.”

She accused him of making “slurs” against Khan, and of trying to align his opponent with extremists.

When I asked Goldsmith about this, he insisted Khan’s past willingness to share platforms with extremists raises questions about the Labour candidate’s judgment.

Goldsmith also lamented that “Labour-generated questions about racism” were designed purely to silence him, and were edging “all the positivity” out of the campaign.

Activists fanned out from Wimbledon Station to deliver leaflets. These are targeted at voters who are sympathetic to the Tories, but are by no means certain to turn out.

Stephen Hammond, the local Tory MP, accompanied Goldsmith down various streets, as did the BBC camera crew and various other journalists.

Politics under these circumstances becomes too artificial to draw any firm conclusions. We were calling only on households which were likely to vote Conservative, so the Labour response became impossible to gauge.

Goldsmith lit a heat stick –  a device for producing tobacco-flavoured nicotine vapour – but placed it in his pocket before knocking on doors.

His chief role at this late stage of the campaign is not to meet voters, but to sustain the morale of activists. From Wimbledon, he went on to Putney, where he met a crowd of about 50 Conservatives outside Waitrose.

It was here that he encountered not only Justine Greening, who is the local Tory MP, but Charlie, the Cocker Spaniel, who was wearing a Tory rosette and was delighted to be held in the candidate’s arms.

For Goldsmith possesses an unforced ease with domestic pets. When he visited, some time ago, my part of London, he was photographed with a parrot.

The mood of the mayoral contest has since darkened. As the late, great Alan Watkins used to remind us, “politics is a rough old trade”.

But one hopes the present exchange of insults, though distressing to high-minded people, will have the useful result of clarifying how far a candidate can go while being spared any imputation of sympathising with terrorists.

The anti-semitism row should, similarly, help to show where the boundary lies between criticising Israel and expressing vile anti-semitic prejudice.

This process of clarification may be unedifying, but it is necessary. If Goldsmith had remained, throughout this campaign, immaculately reticent and well-mannered, he would have been dismissed by the commentariat, and indeed by the electorate, as hopelessly ineffectual and effete.