There's Goldman Sachs, the Sugar Cane Lobby, non-profits that raise money against childhood obesity. It'll really be voting with wallets.
And I think Goldman Sachs wins that fight every time. Which is the whole purpose - to let the smart money guide the policy.
And even if that was the case - define smart. Smart in the interest of Goldman Sachs is to make more money. Smart in the interest of humanity, society or a community can be (and often is) something entirely different. Who are we creating policy for?
Eventually it does. Manipulating markets == handing your money to someone else, so the rich manipulators will exponentially [1] lose money as the smart speculators take it.
In this case, it's "smart in the interests of predicting which policies achieve the democratically selected objective function". For example, smart in predicting whether Obamacare will bend the cost curve (assuming that's the goal of obamacare).
[1] Assume 50/50 bets. The speculator bets $1, and takes $1 from the rich man. Next bet, he bets $2, takes $2 from the rich. Next bet he bets $4. The rate of growth doesn't have to be ln(2), but it is exponential.