I like to believe--or at least fantasize--that bipartisan alliances can be built around a shared commitment to Good Equations in Public Policy, even if they disagree on what those policies are.
"Look Bob, I think your tax cut proposal is pure pork and regulatory capture, but that one one goddamn sexy curve."
So the plan that passes is the one that claims to help people (appeasing the first group) while also costing the minimum amount of money (appeasing the second group). The proposal with evolutionary fitness in politics is then to create a system that helps people on paper but actually limits eligibility for the system to a minimum number of people or otherwise makes use of it more arduous to deter usage so it costs less. Extra points for making it so complicated that people don't realize what's really happening so they don't object if it doesn't really do what they wanted.
But there is also a level of incompetence/inefficiency here, because the complex and overlapping systems that pass as a result often have high overhead that waste tax dollars, or create bad incentives because nobody thought them through and those incentives create deadweight economic losses adverse to the interests of even the people who want to minimize taxes. As the obvious example, if you create a system with welfare cliffs and then people have the incentive to stay on welfare instead of taking a job, you now have more government expense and lower tax revenue than a system that doesn't do this.
At which point there is a Pareto-optimal improvement on the table if you can get the bill passed.
In general, no policy, like none at all, should be designed to suddenly come into effect when you hit a constant. All functions should be smooth.