What are the merits and demerits of a multi party system of government?

A multi party state exists where we have more
than two political parties. Nigeria has always been a
multi-party state apart from the
period .of the Babangida ill-fated and doomed transitional programme that produced a two party state. 

MERITS OF MULTI
PARTY SYSTEM 

1. Multi Party System is very
   democratic. This is because, it allows all shades of opinions to
   be represented in the legislature and it also assists in
   accommodating diverging views.
2. Multi Party System checks against
   the domination of the political scene by only one party. this also assists in reducing despotic
   tendency and, authoritarian approach.
3.  Multi Party System tend to
   promote competition among the various political groups. There
   is competition in terms of programmes and manifestoes to
   offer to the electorates and also in terms of geographical
   competition for followership and support.
4. The electorates have the maximum
   freedom to choose between the various competing
   parties. Therefore it can be said that multi-party system
   helps to accommodate different shades of opinions.
5. Multi Party System also checks
   against dictatorial tendencies of one party state.

DEMERITS OF MULTI
PARTY SYSTEM.

1. It can produce instability: A multi party system is highly prone to instability most especially in a
   parliamentary system, if  there is no party with a clear
   majority to form the government, it can lead to fragile coalition.
2. There may be weak opposition from
   the opposing parties. The winning party may device manipulative
   tendencies to prevent opposition from other
   parties.
3. Multi party system does not promote national unity hence, it polarises the society into different camps. 
4. It is expensive in term of resources to
   operate multiparty system successfully. 
5. It
   can also lead to the emergence of tribally based political parties. This was the case in the first and
   second ‘republic in Nigeria when the political parties that
   emerged were all tribally based.