The US Congress was established by the 1st Article of the Constitution. The founders enumerated a litany of powers, such as the power to coin money, establish a post office and raise taxes, as well as a basic structure. For example, Congress was established as a bicameral legislature (primarily as a compromise between larger states and smaller states during the constitutional convention). Each house has its own leadership structure which is elected by the members of that house. Legislation can be introduced in either house by a member of congress (non-members, such as the president, cannot introduce legislation).
This legislation is considered in a committee or subcommittee, which makes amendments and changes based on testimony and discussion (known as the markup phase). Legislation that is recommended to the chamber is debated on the floor, with individuals on either side of the issue giving speeches. The debate is controlled by the respective parties who allocate a block of time to those who wish to weigh in. A vote is then taken on cloture, which ends the debate and moves the bill to a floor vote. One way that a minority party can have a say in the legislative process is by “filibustering,” or preventing a vote on the issue by refusing to close debate.
Previously, this could only be accomplished by literally refusing to yield the floor, and constantly talking (some members read novels and phonebooks); now, it is simply a voting procedure. Once the legislation has passed the House and the Senate, it is likely that each respective version will be substantially different. At this point, a conference committee is held in which differences in the legislation are ironed out, and then re-voted on. The legislation is finally forwarded to the desk of the President. If he signs it, the legislation has officially become law; in the event of a veto, the legislation returns to congress where they must now override the veto with a 2/3 majority. Congress has several ways of interacting with the other two branches of government.
Confirmation is the primary power vested in the congress to oversee the Executive and Judicial branches. When the President appoints individuals to serve in his cabinet and in other executive positions, the selections must be approved by the Senate. In certain recent cases, this process has resulted in a change of nominee; Tom Daschle was nominated to become the Secretary of Health and Human Services but withdrew his name after-tax issues came out during congressional hearings. Similarly, Congress must approve judges nominated to the federal and supreme courts.
An infamous example occurred when Ronald Regan’s nominee for the Supreme Court, Robert Bork, was not confirmed by the Senate. Beyond controlling the access points to positions, congress can also override a presidential veto with a 2/3 vote. This feature prevents a president from exercising power so unwieldy that he could grind any attempts by congress to a screeching halt. Furthermore, Congress has impeachment powers, which can lead to the removal of the President under dire circumstances. While this power is not frequently used, it hypothetically is a check on the Presidency devolving into demagoguery.
The Founding Fathers would most likely be bewildered at the form that the government has evolved into, but probably not too disappointed in the operation of checks and balances. Several structural changes in the way Congress operates would most likely come as a surprise. For example, the fact that Senators are now elected by a popular vote ran against the original conception that they ought to be more immune from the pressures of the popular vote, and by extension better equipped to make objective political judgments. Yet, the major component that they would have not anticipated was the political parties.
As originally conceived, there was no place for an organized party structure in the United States government. However, James Madison famously wrote in the Federalist Papers that factions inevitably emerge, which is why a government with checks and balances would be necessary. The only problem with Madison’s theory is that if one faction becomes so large and powerful that they are able to exert control over all three branches of government. In that scenario (which has occurred fairly frequently over the last few decades), there are few real checks which would prevent the government from taking extreme action. For example, under the Bush administration when Republicans controlled congress, several policy positions were instituted unilaterally, such as the invasion of Iraq and the warrantless wiretapping program.
Along with the same circumstances, the recent Obama administration has been able to get a tremendous amount of legislation passed which includes a dramatic remaking of fiscal policies. Both of these instances demonstrate that the checks and balances only function if one faction does not become so large that they control all three outlets of power.