If a politician is on the national (or even State) leve, then yes they lie. They have to in order to "move up" in the world of politics.

You can find some good politicians on the local level, but in order to move up, you've got to become part of the corruption (or you just don't get the support needed at the next level).

(As an aside, that's why Trump is such a threat--because he didn't come up through the system, he never owed anyone "favors" along the way, and consequently he's not "owned" by any political party...)

But in summary, all politicians are corrupt.