If there’s anything all Americans revere, it is the Constitution.

From raw recruits to the president of the United States, virtually all who hold public office pledge to “preserve, protect and defend” it.

This venerable document, adopted in 1789, is the nation’s civic bible.

Yet despite all the respect for the Constitution, Congress informally amends it, undermining the democratic principles it embodies.

The prime example is the filibuster — a potentially endless talkathon — and related procedures blocking majority rule in the U.S. Senate.

Though there are only a few matters where the Constitution requires more than a simple majority vote, the Senate routinely requires 60 votes to do any serious business. It takes that many votes to stop a filibuster.

And a single senator can put a “hold” on a presidential nomination, effectively blocking it from coming to a vote.

At the start of each new Congress, the Senate adopts its rules by a majority vote. In January, the majority Senate Democrats will be able to stem this unconstitutional drift, and some reforms may pass.

The minority may be denied the right to filibuster even starting debate on a bill. And the use of one-person “holds” may be limited.

The Democrats deserve some blame, having blocked proposed Republican amendments to bills from being debated. So perhaps if they allow Republican proposals to be debated, the GOP will cut back on filibusters.

But the filibuster itself will probably not be modified much, leaving that informal constitutional amendment in place.

So much for majority rule.

Another problem comes in confirming presidential appointments, which constitutionally requires a majority vote of the Senate.

Using the filibuster or putting holds on nominations, a minority party can prevent a president from putting his team into key offices.

But the Constitution allows the president to put people in office without confirmation “during the recess of the Senate.” Such appointees may serve for a limited period.

At the time this provision was adopted, Congress was away from Washington a good part of the year. Now it is in session almost all the time.

But not quite all, so presidents from George Washington through George W. Bush used socalled recess appointments to bypass extended congressional inaction.

Facing President Obama, minority Senate Republicans have resorted to keeping the body in session using parliamentary maneuvers. The Senate was really not doing any business for weeks at a time. Only one senator remaining on duty can prevent a recess.

Obama, saying this action was a ploy that could not disguise what really is a recess, started ignoring the phony sessions and has made recess appointments.

The courts have been asked to decide which side is right, but they are usually unwilling to settle political disputes between the other two branches of government.

Speaking of courts, Congress has taken to trying to tell them they have no jurisdiction over some matters, contrary to the Constitution.

For example, one law denied courts the right to review matters relating to the Guantanamo detainees. The Supreme Court overruled that law under its power to determine if laws are constitutional.

Recently, in considering the proposed ratification of a treaty to set as a worldwide standard the same treatment of handicapped people used by the United States under the Americans with Disabilities Act, known as the ADA, the vote contained a proviso that the treaty could not be used by the courts.

In other words, the ADA itself could be cited in court, but judges could not refer to the international standard that was identical to and based on the ADA.

In the end, this assault on the courts did not matter, because the Senate, needing a two-thirds vote under the Constitution, fell a few votes short. Republicans split on the vote, but only GOP senators opposed the treaty. Maine’s two senators supported it.

Among the grounds used by opponents was their belief that the treaty would limit the sovereignty of the United States. But that’s the whole point.

Treaties are part of the “supreme law of the land,” according to the Constitution. Because treaties may contain international obligations affecting the country’s freedom of action, the two-thirds, supermajority vote is required.

If enough senators refuse to accept the fact that ratifying any treaty is a sovereign choice to accept an international obligation, the United States could end up ratifying no more treaties.

In all these cases, federal officials have distorted the clear meaning of the Constitution to suit their immediate political objectives.

If Congress continues to ignore the most basic rules of the game, the danger is there won’t be any rules left that all Americans can accept and respect.

GORDON L. WEIL, of Harpswell, is an author, publisher, consultant and former public official.