For the realisation of the “One Nation, One Election” as has been recently discussed in the Indian context it is suggested that the simultaneous elections of Lok Sabha (Parliament), all the State Legislative Assemblies as well as may be local bodies should be considered.

Possible Gains:

Decreased Costs: If done in parallel, then the accounting on the exchequer would be slashed to a great extent. Manpower cost, security cost and infrastructural cost and all other logistic cost would have to amalgamate here.
Administrative Efficiency: This would also mean that the election processes would be well ordered and that the administrative machine is not overworked by the elections, then available resource can be put to other productive uses.
Minimized Political Diversion: Over and over again the process of elections interferes with governance and development endeavors. Conversely, holding elections at the same time could possibly reduce such a distraction and allow the government to proceed with doing its policy implementation business.
Voter Fatigue: This has been the observation across the democratic systems that have adopted this form of frequent elections because in the long run it leads to voter fatigue and dis. That means it is possible that the voters’ turnout will be increased with the help of conducting simultaneous elections since the frequency of electoral events will be decreased.
Potential Challenges:

Federalism Concerns: India is a federal nation, therefore, it has multi politically dynamic areas. A uniform election schedule may be against the provision of state sovereignty and may affect a state’s capacity to solve local problems.
Political Instability: Once in a while, there may be earlier dissolution of state assemblies or There may be some emergent conditions which may upset the schedule thus posing a threat to the process of political stability.
Dominance of National Parties: I think that the idea of the holding of simultaneous elections is beneficial to the most influential, and therefore wealthy and well–organized national parties, and may prejudice regional parties and regional goals.
Constitutional Amendments: “One Nation, One Election” may need a major overhaul of the constitution which is always a long drawn process.
Practical Difficulties: The idea of coordinating elections across such a large and diverse country with different political calendar and electoral issues would be almost an impossible task.