The wrecking of Clarke’s career makes an interesting case study. He won almost universal praise as education secretary, his first cabinet job. But after his promotion to the Home Office he never looked entirely happy. He was under intense pressure from Blair to take additional powers to detain terrorist suspects and to create new offences, such as the glorification of terrorism.
Much more than David Blunkett before him, Clarke took seriously the arguments of civil libertarians. Even if physically he resembled a round peg, Blair was clearly bashing him into a square hole. Early in Clarke’s tenure it was already rumoured that Blair was dissatisfied.
(You saw the result of Blair's early dissatisaction with briefings to the press that Clarke's days were numbered, leading to Steve Bell's excellent "beserk elephant" cartoon).