It may not be bribary, but is it right?
The bottome line is do these polititions represent the people who paid for their campaigns or the people who voted for their campaigns?
It's fine taking money from lobbyists if you do believe in their goals, but make it clear to the people who are voting what your agenda is.
They should all have to declare as part of their campaign which "special interests" group contributed to their campaign. Then if people still vote for them it's their own fault.