Political campaigns started getting expensive in the 1960s, when television advertising became the next big thing in campaigning. Even before TV, reaching people was hard work. You needed to knock on doors, phone bank, and send out mailings. All of this required a lot of dedicated activists and dedicated dollars. And so politicians depended very heavily on the activists and donors who could provide these things. All of this is in the process of changing. Activists and dollars are becoming less important than they used to be. They still matter, but not as much. And as time goes on, they grow weaker.