Within the general framework of the model of political marketing in economy, political parties achieving their strategic goals tend to treat the economic policy in the instrumental way. The most important is the behaviour of the ruling party that faces the threat of the loss of the power even before the next elections. In order to hold office the ruling party tries to adjust their microstructural policy by following the changes in the current parliamentary configuration and assumable preferences of the voters. Such behaviour, that is characteristic for both opportunistic and formerly idealistic political parties, can be the reason of the instability of the microstructural policy. A possibility of this instability is a characteristic feature of the representative democratic system.