Responsible party government theory.
Party system is said to encourage division.
System in UK in theory:
1. 2 party system with election
2. One forms a govn
3. close competition - urges both parties, oposition can win by legal means
4. parties have manifestos. So electorates can choose between packages
5. manifestos must be popular
6. voters will give rational votes, based on manifestos and previous office records
7. the party who wins puts their programme to action
8. good party discipline in orrder to push the programme through
MPs owe everything to party and must be obediant.

Practice
1. 2party system. Now national parties. Anyway, there have been no minority governments since 79. Because of the first pass the post system the multi party support is turned to single party dominance in westminster.
2. single party govn - some coalitions (liblab pact 77-79), but otherwise mostly one party. 
3. meaningful choice of manifestos - parties have to go for the centre, and they also like to keep theiir policy options open. Labour is said to not offer a good socialist alternative. 70s bought real choice back to elections as the unemployment rose etc(conviction politics). Late 80s other parties had to accept thatcher politics. New Labour developed. Once again electorate is without a real choice.
4. Implementing manifestos - many departures once in office (nationalisation of Rolls Royce), but they are excused. Labour could not implement a socialist regime, because of the secret state and civil service objecting it. Govn not always clear of its objectives or the means of achieiving them. Rose - Heath govn fulliflled 80% of promises, 74-9 Labour o ly 59%.
5. Do voters vote on programmes - Butler and Stokes discovered the limited knowledge of public. People were party loyal despite the manifestos or promises. Issue Voting-Rational Choice model says people purchase politics by voting on the party they like most. Thruth is somewhere in between. People are usually informed of their narrow field. 
Public Choice and Adversary Party Politics.
Theory - is very over politicised. APP - parties get extreme, because the activists are usually extreme in parties. Oversimplification of complex issues into 2 alternatives. Public Choice applies neoclassical economics to politics and consists of:
 a. economic theory of democracy (Downs). Not rational to have ideologies and parties tend for the centre. S-party who is most irresponsiblee in promisses wins, D-unrealistic demands to government from public result.
 b. political business cycles- governments manipulate the economy to be at its best in elections. Remedies - law to balance the budget, election time at random
Practice - These politics now out of date and maybe biased towards right wing. Tories have made a thing out of not aranging preelection booms and intervening with the economy. Gamble and Walkland found little evidence of U-turns. There are 3 policies - foreign, stabilisation and industrial. In foreign divisions between parties have been less than inside parties (wrt EC). Nordhaus has looked at the political business cycles. USA had cycles but UK did not. These cycles did not do much harm nor did they affect voters. 
Is the decline caused by parties? It could be one of many causes. 
 a. UK has been in decline for 100 years, party politics only questionable for 20years. 
 b. Parties are only a part of political system (civil service as well). 
 c. Parties are not free to do what they want.