If they made lobbying illegal

This dilbert cartoon captures my thoughts exactly on what would happen if lobbying was made illegal.
Dilbert CEO Senator Bribe Cartoon
Two things become clear from this:
1) If a politician has some power that is useful to a businessman, he will find ways to bribe the politician.
2) If a politician is willing to be bribed, the politician will find ways to get that money.

We know that politicians will always be willing to be bribed unless of course they belong your favorite party or are angels. Also, I don't think there is any doubt that as long as the politician has power that can help the businessman, no. 1 will be done.

So, the only realistic way of reducing (you can never eliminate) bribes and lobbying to me seems to be to reduce the power of the politician in areas that can benefit a businessman. In other words take the power of economy away from the government and the bribes and lobbying will all but disappear.