It is a three tuple

The best model is Treasury, Senate and House.  Treat these as a closed monetary system.  At any given time any citizen in any district will be equally likely to be screed by one of these three during any given transaction, or con tosses.

I use screwed on purpose, these are account imbalances, mess up that we are minimizing, fewer collisions. The citizen thus, at equilibhrium, has a three sector portfolio he manages with election coin tosses. He is distributing his attention, alternately, between these three with the ballot.

This implies the states and districts have variant flows, stock and flow for the one is relatively prime to the other. These states and districts form separate value chains, each chain trying not to step on the toes of the other.

There are planning errors, known unknowns that can be estimated ex ante. We all sort of know our Planck's constant. That is what we need, a cash market to bet these ex ante error estimates, how much will this screw my state or district in the sense of causing congestion down the path. It is a ratio near one and a positive value of about a third of the federal budget. That is the amount of cash set aside for variance liquidity.

The swap, either way, of cash is not the issue. The elites fear the amount, we really are at variance, ex ante, about a third of the budget. There is interaction time, districts adjusting and states adjusting separately. There is no Godot to allocate the error budget, it is a distributed liquidity issue because the Constitution carves in the imbalance and forces us to  minimize with a self sampled voting system.  These ballots are sectors, we are running an optimum portfolio algorithm in run time.

Central bank cash vs earmarks, the former is by far the better and has a multiplier because it is a market share gain for the Fed, more of the transaction flow appears on their books and it is as smooth as possible, good stuff for the monopoly tax dollar. Combine this with an inflation tax power for Treasury, run the three tuple portfolio, you will be impressed.