[quote=Fat Boy Kyle]
Politicians often have to present to the public the notion that they support a particular set of ideas, not because they believe in them, but because the mentioned ideas are popular and likely to win votes. In the UK (at least) political parties also employ 'whips' who keep their members in check, meaning that unless a MP wants to be kicked out of their party they have to be seen to support (in public and voting) most of what their wider party supports regardless of their own beliefs.
[/quote]

I think everyone has 'whips.' Everyone democratic anyway.

Saying 'Politicians are supposed to lie' is a negative interpretation. Another way of saying the same thing would be 'Politicians don't always get to tell the truth.' We could imagine any number of scenarios where a bad truth is worse than a good lie (Maybe Putin asks the Ukrainians 'Does this drag make me look like I poke dudes?'); part of the responsibility that comes with the bigger offices, is that consequences extend to your people, not just upon yourself.