How did Lord Mandelson become so powerful(UK)?

Despite being elected Labour MP for Hartlepool in 1992 he systematically worked his slimy way against the Party from within. As we all know, Kinnock buggered off under pressure created by Mandleson & his cohorts leaving a clear path for the despicable traitor Blair to take over the ravaged party. The result? A manifestly uber right wing New Labour Party coming into being via the back door. It's been down hill for the electorate ever since owing to the difficulty in distinguishing between them and the Tories. This recent bullying undercover/unofficial leadership role he's achieved illustrates not only how undemocratically corrupt New Labour are but the fact Brown, being the incompetent non-entity his is, failed to notice his authority was being undermined. That is why I, an ex Labour Town Councillor and party activist before resigning 10 years back, shall be voting and actively working for the United Kingdom Independence Party on May 6 this year!