Some very strange things are happening in Buckingham.

The sitting MP is John Bercow. He is also Speaker of the House of Commons. There is a perfectly just tradition that the Speaker is not challenged, and even though a few right-wing Tory backwoodsmen have been plotting undemocratically in Westminster to remove him, they are estranged from their leader. Indeed, David Cameron has said:

John Bercow is a hard-working constituency MP, who continues to take up cases and support local issues. So in this election I would certainly urge all Conservatives -- and, indeed, supporters of all parties and of none -- to vote for the Speaker, John Bercow.

I wrote about the isolated Tory plot and about Bercow's reforms to parliament here. And although I recommend that you read it all, I will just post here the conclusion:

Those agitating for Bercow's removal are few in number, but we should not underestimate their determination. Were their plot to succeed, it would not just remove a reforming Speaker, but threaten parliamentary democracy itself.

Now, however, there is a new threat, from two mavericks, who appear to be trying to take advantage of the anti-politics mood by targeting a man who, ironically, is parliament's best hope for reform following the expenses crisis. Bercow is being got at from the right by the blazer-and-cravate smoothie Nigel Farage, of the Dad's Army party, Ukip. And from the left, we have John Stevens, a former Liberal Democrat and a passionate pro-European.

Now, as it happens, I have met both these challengers, and they are amiable and intelligent. In any other circumstances -- and any other constituency -- they would deserve a decent shot at entering the Commons. But by going after Bercow, they are not playing fair. Farage cannot expect his pressure-group-party to be taken seriously if it seeks to breach an important convention adopted by all three main parties.

As for Stevens, he has just been rebuked by the Liberal Democrats for seeking to claim the support of the Lib Dem spokesman for Buckingham, Marie-Louise Rossi. The chair of South Central Region Liberal Democrats, Steve Sollitt, has issued a statement saying:

We understand that a candidate in the Buckingham constituency has been circulating a leaflet which implies our support. This comment had not been signed off by either our parliamentary spokesperson, Marie-Louise Rossi, or by the Buckingham Constituency Liberal Democrats. The Liberal Democrats are not supporting John Stevens or any other candidate in the Buckingham constituency.

Meanwhile, posters are mysteriously springing up across Buckingham -- "Get Flipper Bercow Out" -- without any official imprint. There is the air of dirty tricks around.

Now, I don't intend to make declarations of support in this campaign. But I am in line with convention by coming to the defence of the Speaker, who anyway is the last person who should be targeted by those seeking to ride the wave of an expenses backlash. Back in May 2009, before he became Speaker, I outlined the progressive case for John Bercow, a man of great independence of thought and a fundamental sense of fairness, and I believe it still stands:

Many feel that Bercow's bold approach to his party could be applied to parliament, and badly needed it is, too.

In January 2002, as shadow chief secretary to the Treasury, Bercow wrote a provocative New Year letter to his Buckingham constituency party. Many voters, he said, saw the Tories as "racist, sexist, homophobic and anti-youth". This observation marked the near-completion of his conversion from right-wing Conservative student and member of the anti-immigration Monday Club to ultramoderniser, years before David Cameron claimed the title of Tory "change" candidate.

Bercow's journey was influenced by his partnership with Sally Illman, an egalitarian Labour sympathiser whom he married in 2002. Yet it did not begin there. Some Tory MPs blame Illman, or "that woman", for his views, but his conversion was first made public on 10 February 2000, when he gave a 13-minute speech in favour of reducing the homosexual age of consent to 16. A month before his wedding in December 2002, Bercow resigned from the front bench over Iain Duncan Smith's decision to oppose the rights of unmarried and homosexual couples to adopt. His alienation from the party intensified when, in 2007, the government asked him to review services for children and young people with special speech, language and communication needs. Since then, he has kept a relatively low profile, becoming as resented by Tory traditionalists as he is admired by progressives in other parties.

. . . For all his despair at the pomp and ceremony of the Palace of Westminster, Bercow remains a House of Commons man to the core. He is a long-time believer in reform, not just in the wake of the expenses scandal, from which he has emerged (so far) unscathed, but in terms of wider, fundamental change. Since his departure from front-line party politics he has focused partly on redressing the balance between the overmighty executive and the legislature, calling in 2005 for select committees to be strengthened by election.

One admirer on the left says Bercow is "a genuine liberal -- as opposed to a paint-spray liberal". But as well as being socially liberal, he believes . . . that "modernisation" concerns fundamental issues such as tax, redistribution and immigration. The son of a minicab driver, with no private wealth, Bercow is, to many of his colleagues, "not one of us". Already there is a campaign to undermine him, led by Tory MPs who are keen to talk up the need for an "interim" speaker, possibly Ann Widdecombe. However, such a compromise would not produce the fresh start needed. These same Tories say that Bercow is too young and hasn't been in the House long enough. Yet, at 46, he is four years older than his party's candidate for prime minister, and became an MP four years earlier, in 1997.

. . . When he wrote his damning constituency letter in 2002, Bercow added that his party was "in worse shape than ever before in my lifetime or yours". Today, the same could be said of the standing of parliament. Traditional Tory hostility to Bercow may in the end prevent him from becoming Speaker, but that he is the true change candidate is not in doubt.

To conclude, I would only echo the words of David Cameron, and say that voters in Buckingham of all parties and none should re-elect John Bercow, who has a great plan of reform that Westminster badly needs. They should do so for the sake of his constituency and for the sake of the future of our national politics.