Although he was himself a Nationalist and secular person he couldn't launch a crusade against communal forces. His policy of firm faith in secularism and democracy was right but also suffered from weaknesses. He failed to use the Congress against communal forces and had to compromise on his principles when Congress allied with Muslim and Christian communal forces in Kerela. He also failed to ensure States took steps in the administration to crush communalism. Riots on religion also occurred during his last years.
Polity of India was democratic in which large number of parties thrived. After independence these parties played a major role in the opposition and managed to win sizeable number of votes in General elections. All these parties were Pan India in terms of objectives and ideology. They had leaders of impeccable integrity and even when the base of the party was narrow geographically but the character was All India. These parties played an important role in Parliament and provided high quality debates on questions of national importance. One reason for this was Nehru's nature of accommodating everyone.
However the opposition parties couldn't unite and so never challenged the hegemony of the Congress till 1977. Opposition parties to the congress would influence it through various agitations and since Congress had a mixture of various groups it was successfully influenced and even absorbed the agitating parties. Sometimes it would lead to opposing parties having a more radical stance to ensure that its base wouldn't be absorbed in the Congress but this meant having an extreme rightist or leftist stance that affected the public opinion of the party and made it vulnerable to splits.
Congress itself saw a major change in structure. It had now to evolve into a party from a movement but this transformation was slow. The Congress was to get a organizational cohesion by Sardar Patel's suggestion that no member of other political party could be a member of congress. This however upset the Congress Socialist party and its members decided to exit. However again Nehru succeeded in placating them and kept the Leftist and Rightist members together while trying to give the Congress a leftist perspective.
This was to be an arduous task as the Congress had a Pan India base and support of all sections of the society. It also believed in ruling through consensus and this meant unifying diverse views. The Congress itself had a democratic structure with multiple levels of decision making at provinces and center.
Party vs Government
Nehru became head of the Interim government from 1946 and this led to his resignation from president-ship of Congress. His replacement Kriplani argued that the President of the Congress should be taken into confidence on government policy initiatives. But this view wasn't shared by either Nehru or his political associates like Patel or Rajendra Prasad. All felt that government must be responsible to the people not a party and should be in control of all decisions related to governance. The Congress should restrict itself to party activities and not demand consultation by the government.
Nehru vs Sardar Patel
Sardar Patel was the Leader of Right wing of Congress. He was a believer in capitalism and free markets but also shared Nehru's vision of egalitarian society. Although both had a tense relationship and offered to resign from government at one point or another but what commonality they had was more important than their differences. Both believed in Gandhiji's leadership and when Gandhiji died both realised the importance of cooperation. Patel argued for Right to Property as a fundamental right and succeeded in making it one. This was firmly opposed by Nehru although he accepted it later.
Patel would argue strongly for a point but if on basis of arguments he couldn't succeed in convincing Nehru he would accept Nehru's view. Patel's though was a great organizer and able administrator but lacked Nehru's mass support and wide social and developmental perspective.
Sardar Patel was the inspiration behind creation of Indian National Trade Union Congress.
Nehru vs Purshottam Tandon
This conflict was mainly a fight between the Rightist and leftist wings of the Congress. Nehru had supported Kriplani as the Party president indicating that working with Tandon who was a Right-wing candidate supported by Sardar Patel would be difficult for him. In the elections, Kriplani won and Nehru offered to resign but Tandon accepting Nehru's important role in the forthcoming elections resigned and Congress Working Committee offered president-ship to Nehru. Although Nehru felt that a Prime minister should act as President of Congress but he accepted.
Nehru - Tandon conflict was also related to the old issue of Party vs Government. Party wanted the government to be implementing the party policies. However the government wanted full control over its working. This system was followed in most democracies but in India wouldn't be suitable as Party had deep roots even in villages and thus could act as interfaces of people to government. They would be useful in gauging public opinion and keeping a check on bureaucracy. The party leaders would decide who could contest on a party ticket and so decide indirectly future government leaders.
One important failure of Nehru was not recognizing importance of party work and relegating party cadres to unimportant positions. This led many cadres to ignore party work which was essentially mass mobilization and focus only on becoming parliament leaders.The cadres would take up party work only when left out of Government posts and this too only to gain popularity and reenter Government.
The Communists had left the congress in 1945 and ideological differences emerged against the Socialists in post independence period due to Sardar Patels "One Party membership rule". This led to their walking away from the Congress. This made congress to become controlled by Right-wing or conservatives.Nehru himself was in favor of Socialist policy and wanted to make the Congress a "Left of Center" party. However differences emerged between him and Socialist leaders later on. Nehru attacked their ideology and the Socialists accused him of abandoning his principles and becoming partisan.
Although Socialists never were a grave threat in the opposition and their radical stance against congress gradually led to erosion of their public support and splits but Congress was facing other problems too. The leaders that had risen during independence struggle couldn't organize the party post-independence and so new leaders didn't emerge. Next generation saw congress as a party of no strong ideology and preferred joining the opposition. Nehru though a great Nationalist was never a Party organizer and so couldn't stem the rot.
Second problem was that power had seduced many of the leaders. The cadres were now mainly interested in power and neglected party work. Government though belonged to Congress but those in power too neglected to see the important role the party could play in gauging public opinion of the government. This led to atrophy.
Thirdly, as Socialists and Communists left the party the conservatives stepped in. The Congress now took stands in favor of capitalism and isolated its old support base. Even where agrarian reforms and other socialist policies were decided, failed to gain support and had to be abandoned.
A late plan of reform was decided by Nehru and K Kamaraj known as the Kamaraj plan. This meant that all Congress leaders in executive roles would resign in favor of other cadres and focus on party work. This would revive the party. But this reform arrived too late and Nehru's death in 1964 meant that it couldn't be implemented fully.