Has George Osborne just cost Zac Goldsmith the London mayoral election?

In 2012, most opinion polls suggested that Boris Johnson would win the London mayoral election by a landslide. Part of the reason he didn't was because of public anger over George Osborne's "omnishambles" budget. Osborne's cuts to the top rate of tax, while cutting benefits for the worse off, was a major error that hurt the Tories' polling position for years to come.

In the end, Boris came fairly close to losing that year, with some of his senior team convinced they had fallen short early on in the night. As the results came in, Osborne's name was cursed by a number of Johnson supporters in City Hall.

Now history looks to be repeating itself. Several polls in the past few days have shown Osborne's budget this week has put a dent in support for the Tories, with one poll today showing Labour with their first lead since the general election. If Zac Goldsmith does fail to win in May, Osborne's budget could prove to be one of the biggest reasons why. Ongoing Tory infighting over Europe, which Zac has partly helped to fuel, could also be a factor.

It wasn't supposed to be this way. Goldsmith's supporters had been expecting a significant boost from the budget, following announcements about Crossrail 2 funding and business rate devolution. They hoped the announcements would put further pressure on Khan over his funding of a fares freeze. A joint photo shoot with the chancellor was even conducted in advance, with the aim of associating the Conservative candidate with Osborne.

That now looks to have been a mistake. A poll today found that more people thought Osborne's budget was unfair than those who thought it was fair – the first time since Osborne's disastrous budget in 2012. Most unpopular of all was the chancellor's decision to slash benefits for disabled people by over £4 billion. YouGov found that 70% of the public believe this was the wrong priority, compared to just 13% who believe it is a good idea.

The budget is also putting pressure on Goldsmith himself. His support for disability benefit cuts has become a big local issue for the Conservative candidate, after he was axed as the patron of a disability charity in Richmond. Today the Richmond Times splashed on a story about Zac's removal from the charity with the headline: "Hit the Road, Zac". Goldsmith often likes to boast in hustings that his increased majority at the last general election shows he is appreciated by his constituents. That now looks like a harder line for him to sell.

Goldsmith's chances of winning are still significantly better than the polls and most pundits suggest. Many of the measures in Osborne's budget could prove to be popular in the outer London boroughs Goldsmith hopes will carry him to City Hall. It's also worth remembering that Labour's national position in the polls in May 2012 was significantly better than their national position now and yet the Tories still won the mayoralty.

However, in the past four years Labour's overall position in London has improved and in order to win, Zac needs to overcome Labour's big advantage in the city. The signs from the budget this week are that this advantage has just got bigger.