Michael Gove is the unexpected star of the coalition's first 21 months. The contrast with Andrew Lansley flatters the Education Secretary, but even if the health Bill had been only a mitigated disaster, Gove would be the winner. Other departments have had mixed results. Iain Duncan Smith's welfare reforms are ambitious, but they have hardly started yet. This week, the welfare Bill should complete its passage through the House of Lords. It will bring in the cap on total benefits, which is popular, but also a vast simplification of the system, called Universal Credit, which is bound to go wrong. Meanwhile, the most notable change made by the Department for Work and Pensions has been a work experience scheme for people claiming Job Seeker's Allowance, which has not yet been a public relations triumph.

Who else? Theresa May has done a surprisingly good job at the Home Office. Her recent insistence that she knew nothing of immigration officials waving people through the "goodness this is a long queue" channel at Heathrow had all the qualities of a broken-down bulldozer. She could not be moved, but you would not say she was engaged in anything useful.

Eric Pickles, the Local Government Secretary, is a good populist, worrying about bin collections in such a way as to make it look most peculiar that the Liberal Democrats, once the pavement pounders of local politics, should appear to be more interested in reforming the Lords. But most other Conservative ministers are too new, or are in departments where it is hard to make an impact, or are Kenneth Clarke.

Then there is George Osborne. His power as David Cameron's real deputy – as opposed to William Hague, deputy "in all but substance" as well as "in all but name" – is unchallenged. He has not had a bad start as Chancellor. But he has not had a good one, either. Paradoxically, low growth may not be a vote loser for the Government, but the failure of the economy to carry on along the bumpy path to recovery on which it was set by Gordon Brown can hardly be called a success.

Compared with all these, Michael Gove is the most successful minister. After an unpromising start, in which he stumbled into several booby traps laid for him by that most small "p" political of opponents, Ed Balls, he has done well. Balls left a stack of IOUs to schools called the Building Schools for the Future fund. When Gove cancelled them, there were local outcries. Gove had problems with cutting a schools sports programme, a decision that he had to reverse. The take-up of his "free schools" policy was low, with the early months dominated by parents asking why they should spend all their spare time to run schools, and there are only 24 of them so far.

But he kept his balance, and has made more important changes that promise to accelerate the improvements in schools already under way. Like Lansley, he did a lot of policy work in opposition, but unlike Lansley he was ready with a Bill straight after the election. As well as pushing ahead with new academies, he allowed existing good schools to convert. By the next election, most secondary schools will be academies. Suddenly, good schools are forming academy chains so that leadership and innovation can be shared, and more and more difficult schools can be turned round. Many teachers and at least one so-called liberal newspaper still don't like academies, but the first wave has improved standards and I think the gains will spread and the evidence become irrefutable.

In an interview in Standpoint magazine last week, Gove set out his ambition thus: "I hope that thanks to the reforms we've introduced the next Guardian editor but three will be a comprehensive school boy or girl."

That interview was also interesting for the deftness with which Gove dealt with the grammar-school mob in his own party. Lapsing into the third person once removed, he said that the Prime Minister "doesn't believe in academic selection".

Nor are Gove's successes confined to schools policy. He has been an important part of Cameron's effort to open up and speed up adoption. Last week he spoke on television about his love for his parents, who adopted him at the age of four months, and in almost socialist terms about how it "haunts me" that so many children's lives are decided by chance.

It is his success as a departmental minister, though, that raises the question of whether he might ever succeed to the top job. Gove is one of the most courteous people I have ever met, and courtesy goes a long way in politics. He has a confidence and an ideological clarity that make him formidable. That ideology is the purest essence of Blairism, which might not be obviously popular but which has the advantage of being right. In a virtuoso speech to the parliamentary press gallery last week, without notes, he said he was proud to be a Blairite, a species that could survive only in the hothouse of government, and which was "now extinct in the wild – that is, in the Parliamentary Labour Party".

Against all that, he has one weakness. He is not a retail politician on television. But if he goes on doing a good job of government, that is the kind of perception that can be turned round, and his peculiarities of manner could become strengths of "a character".

In August 2007, when I asked him if he might one day become Tory leader, Gove quoted Boris Johnson, saying that there was more chance of "my being reincarnated as an olive". Last week, he told Standpoint that he was "constitutionally incapable" of it. Yet it is possible to see how Johnson or Osborne might not be the first choice to succeed Cameron when a vacancy arises. The other day I suggested that Gove should be moved to sort out the disaster of NHS reform. But that may not be the limit of what he can achieve.

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