When I was at university, I had a friend who was in the SWP. Even after she left the SWP, she continued to regard herself as a revolutionary socialist, and for a while she behaved like one. If anything, she had a slightly sectarian bent, criticising myself and other socialists who were members of the Labour Party. (This was 1999-2003.)
This friend was very, very capable indeed, and got herself elected student union president at the head of a Labour Club-initiated slate. In the run up to and during the campaign, however, she began to change. Without formally admitting any shift in her politics, she made all kinds of pretty unprincipled deals and manoeuvres and compromises; being very clever, she always found a way to explain herself in Marxist terms. After she was elected she moved fast to the right, allying with conservative bureaucrats in the union, attacking the left, generally depoliticising things - and being very unpleasant to her former comrades in the process.
When, the following year, I ran for SU president as the Labour candidate, it was widely known that she devoted herself, as the full-time incumbent, to supporting my Blairite opponent's campaign and undermining mine, using all kinds of dirty tricks. (I got 1,100 votes, but lost by a huge margin. Oh well.) During this process, she repeatedly denounced me - a member of a small revolutionary socialist organisation - as a careerist to anyone who would listen.
Still, on some level, I regarded her as one of us - a person of the left, maybe even a socialist in some sense. It was only the year after that, when she made the effort to come back to Oxford from her full-time job in London, to campaign for a Tory against another leftish Labour candidate she disliked, that I finally realised what kind of political creature we were dealing with. This was someone for whom careerism and personal animosity over-rode any commitment to political principle or ideas. (In this case, I suppose, animosity got the better of careerism: not that Millbank would have cared about our left-wing Labour Club getting beaten.) When I challenged her about her support for the Tory, she repeated the accusation of careerism again.
So I was amused to read on the Telegraph website that this woman is now Gordon Brown's chief speech-writer and a leading New Labour apparatchik. Nice one, comrade.