I think the incumbent's governance should be seen as the carrying out or application of their campaign promises or theory. So the incumbent's governance is the real-world test of whether those campaign promises are beneficial or harmful in practice. If governance is harmful, then we should not support a political party that continues to support those campaign promises because we have empirical evidence that their theory is flawed.

It depends on whether the campaigns were realistic in the sense that they were reflecting the actual needs of the voters, the national priorities and agenda plus the resource base of a particular country. I think you will agree with me sometimes some campaigns have been very wishful and ambitious to the extent of just putting forward some promises which are difficult to realize. In such circumstances incumbent's governance has no way than getting back to the drawing board and come up with ideas which are reflective of the actual context.

We can see winner of elections in two ways: either as represenatives of the majority ideas, or as trustees. In the first case governments should carry out the promises of the electoral campains, since the voters decided that that set of political proposals and beliefs was the best suited for the challenges the country will face in the timeframe the government will hold power. In the second case people are electing people they trust will make the best decisions and therefore elected officials have more room to develop completely new ideas, so long they do not breach the public trust (corruption, incompetence etc)

Yes, the way one governance, particularly in African countries are largely based on their manifesto which they had promised to implement if elected. Since most of them want second term, they will always ensure that they fulfil on their pre-election pledges.