So, if I understand you correctly, a rational person:
1. Defines goals.
2. Acts in a reasonable way in order to achieve them.

However, only in hindsight is it possible to say what was a "reasonable" way to act. When the moment comes to take a decision, many wise advisors have contradicting estimates as to the probability of different scenarios, and thus there are many possible "rational" decisions.

So, when trying to judge whether a decision is reasonable, it is necessary to consider the cognitive limitations and emotional state of the decision maker. This includes the attempt to understand the actions of politicians.

But apart from this, I can summarise my stand, that is perhaps not far from yours:
1. The goals of politicians are both personal (e.g., getting lots of power and influence) and national (e.g., the long-term survival of the state of israel).
2. Politicians set their interim goals on the national level in a different way than most people do, and are less affected by commonplace ideology.
3. They do their best to ignore their emotions and biases when taking decisions - something most businessmen also try to do.
4. Politicians use ideology as a tool to influence other people emotionally, without revealing their true goals.

As for the "good" political system - I send it as a separate comment below.

No. I don't. Ever heard about intuition? Didn't you mention "sharp political senses" before?
When brokers are asked why they bought a certain share, they often respond "gut feeling".
Or, let's take chess: How come Gary Kasparov can evaluate a chess position on the fly, but is unable to fully explain his judgement in words?
To summarize, if you cannot explain a decision unambiguously with words or symbols, it ain't fully rational.

If you are willing, I suggest we try to establish an alternative basis for a theory on how politicians act - just as an exploration.

First of all, let's separate the statesman from the politician. For an illustration of a typical politician play in your head the wonderful series "Yes, Minister" (later, "Yes, Prime Minister"). Here we have a person without any understanding in professional areas like finance, health, security - thus being unable to rationally weigh any alternatives and form a meaningful opinion. His asset is a feeling for what the public wants and what rival politicians are concocting - in other words, "sharp political senses".

The statesman, on the other hand, is somebody that has a vision, or at least an understanding of the subjects he is supposed to promote.

So, does our discussion refer to the statesman, or to the politician?