'Divided parties don't win elections'. How valid is this view in explaining Conservative ascendency over Labour in the years 1951-64?

Labour had problems within the party in 1951- Labour figureheads Stafford Cripps and Ernest Bevin had to stand down from the government due to ill-health, Attlee also suffered bouts of illness.

The Conservatives won the general election in 1951 and remained in power for the next 13 years, winning the next two general elections in 1955 and 1959. The election was won with Churchill (1951-55) replaced by Anthony Eden (1955-57) who was later replaced by Harold MacMillan (1957-63). There are two main arguments to this question, the reason why the Conservatives remained in power or the reasons why Labour didn't regain power?

Reasons why Labour were defeated in 1959 due the division in the party?

Labour fell from power in 1951 due to division in the party. Morrison (and the majority of the party) wanted consolidation, whereas Bevan and Labour fundamentalists wanted further reform e.g more more nationalisation. Gaitskell introduced charges for dentures and spectacles and Bevan resigned alongside Harold Wilson and John Freeman. The split between 'moderate' and socialist/leftward leaning in the party made the election campaign weak. 

Most of its ministers (those with experience) had been in office for at least 10 years, old age and illness weakened the party. ''Labour had run out of steam''

Antagonism between Bevanites and Gaitskellites came from different views of how Labour should get back into power. Bevanites opposed what they thought was a retreat from Socialism. Gaitskellites were adament that conditions of British society had changed and Labour had seen beyond Clause Four and support the working class. Neither offered positive policiers for the future other than defence and abandoning Clause Four. 

Defence Policy- The official Labour line was to go along with the government's rearmament in an attempt to keep up with the USA and USSR, Bevan and his supporters- criticised it bitterly; Bevan was on the verge of being expelled from the party after his attacks on Attlee. 'Bevanites' were a continual source of trouble to the Party leadership. Bevan himself resigned from the shadow cabinet in 1954 because he refused to support the creation of South East Asia treaty organisation. (SEATO). In April when he was so openly critical of Attlee in a debate of defences policy that a majority of the Labour party MPs (141 to 112) voted that the Party whip should be withdrawn from him. When Attlee resigned the party leadership in 1955, Bevan's conduct virtually put him out of the running. He gained only 70 voted compared to Gaitskell's 157.

Bevan himself, whose name was attached to all those of the critical left-wing stance towards the party, was unable to provide clear leadership for the left- Lacking a central unifying organisation, they stood little chance of making a significant impact upon party policy. He was also nearly expelled when he refused to support the manufacture of the hydrogen bomb (1955). In the 1957 conference, he attacked unilateral disarmament, which was a devasting shock to those who trusted in Bevan's support for unilateralism. One Bevanite…