Polarizing political statements – what’s the deal?

What do politicians really want to achieve with certain statements?

Example 1: Hillary Clinton recently said that if Iran were to attack Israel during her presidency she would basically destroy Iran: “ I want the Iranians to know that if I'm the president, we will attack Iran...In the next 10 years, during which they might foolishly consider launching an attack on Israel, we would be able to totally obliterate them."

Example 2: (brought to my mind by the global warming thread) Suddenly all politicians seem to agree that global warming is bad.. any hidden scheme?

Now when I hear Mrs. Clinton’s statement or other crass statements I wonder what the politician really wants to achieve with it.

IS it to attract a certain clientele of voters? Saying “we will obliterate Iran” is pretty heave for just that.

Is it because they REALLY believe in it and just want to make it clear?

What are the different reasons for different political utterings? Examples are welcome, interpretations of my examples as well!

Cheers,
Melissa