From The Atlantic, How American Politics Went Insane by Jonathan Rauch

The Constitution makes no mention of many of the essential political structures that we take for granted, such as political parties and congressional committees. If the Constitution were all we had, politicians would be incapable of getting organized to accomplish even routine tasks. Every day, for every bill or compromise, they would have to start from scratch, rounding up hundreds of individual politicians and answering to thousands of squabbling constituencies and millions of voters. By itself, the Constitution is a recipe for chaos.

So Americans developed a second, unwritten constitution. Beginning in the 1790s, politicians sorted themselves into parties. In the 1830s, under Andrew Jackson and Martin Van Buren, the parties established patronage machines and grass-roots bases. The machines and parties used rewards and the occasional punishment to encourage politicians to work together. Meanwhile, Congress developed its seniority and committee systems, rewarding reliability and establishing cooperative routines. Parties, leaders, machines, and congressional hierarchies built densely woven incentive structures that bound politicians into coherent teams. Personal alliances, financial contributions, promotions and prestige, political perks, pork-barrel spending, endorsements, and sometimes a trip to the woodshed or the wilderness: All of those incentives and others, including some of dubious respectability, came into play. If the Constitution was the system’s DNA, the parties and machines and political brokers were its RNA, translating the Founders’ bare-bones framework into dynamic organizations and thus converting conflict into action.