perhaps some game theory needs to be applied
they need to be dependent on your support. it isn't support and they'll honor it, but they have to fear that you might take away the support they now feel entitled to
they're politicians!
Discussion
we need more bribes so we can demonstrate their effectiveness
the initial bribes were too little to be effective
we assure you that your bribe size is getting closer to the effective amount but don't wait too long to get there or the size may need to increase even more