Checks and balances were politically important, which is to say that they were a vital feature of Jeffersonian ideology, which more or less dominated US const'l thought from 1800 until the Civil War. The essence of this ideology was that govt power was always potentially tyrannical and therefore should be kept to a minimum and constrained through various countervailing institutions. When you ask for cites, it's difficult to know when this principle was not uppermost in mind of American politicians.
BTW, Hamilton was not a believer in checks and balances, nor were the Radical Republicans, which is why both were so interesting. Instead, they believed in the concerted power of govt to accomplish their program.
Dan Lazare. <<
As for checks and balances and separation of powers, these doctrines
> were vitally important throughout the antebellum period.
Case cites, please. I can't recall any significant cases where theese were
an issue. Recall that seperation of powers concerns intra-federal,
branch-branch relations, to be distinguished from what we call federalism,
concerning state-federal relations.