john major resigned as leader of the conservative party soon after he was defeated in the general election and clarke stood for election to replace him as leader and therefore become the leader of the opposition. however he was defeated by william hague in this contest. when hague himself resigned after losing the 2001 general election clarke again stood for leader but was defeated by iain duncan smith. in 2005 he stood for the leadership for a third time but was defeated by david cameron. it is thought that clarke was unable to become leader because many in the conservative party do not wish to see the united kingdom replace the pound with the euro as the main currency whereas clarke has always been very much in favour of this policy.