I think that politicians tend to be very pro-social people who attempt to increase the welfare of the groups they belong to, usually quite rationally.

Their groups will be numerous, and of varying importance - including their nation, the voters in their district, the members of their class, race and religion, their colleagues, their own family... and then some.

Lobbyists attempt to be part of the politicians' groups, preferably as many of them as possible. They also bring in money, but they style themselves as brokers, or people who know people and carry favors, because they need to be liked and nobody likes a briber. Non-politicians mostly see the money, and think it is all about that, much like they mostly see what a politician is against, while most politicians chiefly see themselves as people who are for something.