President Barack Obama is scheduled to present the State of the Union address Tuesday night, a tradition as old as the Constitution, but one open to interpretation.

There are very few rules governing and even fewer defining the nature of the State of the Union. Mostly, it is based on precedents and traditions of past presidents.

Article II, Section III, Clause 1 of the U.S. Constitution states a president “shall from time to time give to the Congress information of the State of the Union, and recommend to their consideration such measures as he shall judge necessary and expedient.”

Notice, though, there is no stipulation that the State of the Union be an annual affair, only “time to time.” It is not mandated.

Traditionally, as it is this year, a president gives the speech on a Tuesday, but this is not mandated either. In recent years, Obama gave the State of the Union on a Wednesday evening.

Notice, too, constitutionally, there is no reference to the State of the Union being a “speech.” The president is only required to occasionally provide information on the state of things and his recommendations to handle these matters. It can be a written report sent to Congress, which it was from the presidency of Thomas Jefferson, who felt a speech before Congress too closely resembled the British monarchy’s “Speech from the Throne” to open sessions of Parliament,

 to Woodrow Wilson, who resurrected giving the speech directly to Congress as Presidents George Washington and John Adams had done. Only a few presidents since Wilson have opted to give what was known throughout most of American history as the written “President’s Annual Message to Congress” instead of a speech.

The reason Jefferson settled on a written message is that he believed congressmen may perceive observations as a royal command rather than recommendations if spoken directly to them from the president’s mouth. With the schism of bitter rivalries within the federal government in what would become the American system of partisan politics, Jefferson may have also believed his presence before Congress would serve as blood in the water. Perhaps, a worry that an opposing politician may yell, “You lie,” which Obama endured a few years ago.

“By sending a message, instead of making a speech at the opening of the session, I have prevented the bloody conflict (to) which the making an answer would have committed them,” Jefferson wrote. Not wishing to give the appearance of royal edicts, Jefferson’s State of the Union messages were intentionally vague in their recommendations. Several subsequent administrations followed Jefferson’s vague approach in their annual messages to Congress.

Abraham Lincoln used a written State of the Union message to spell out his plans for the Emancipation Proclamation. “Fellow citizens, we cannot escape history,” Lincoln wrote. “… the fiery trial through which we pass will light us down in honor or dishonor to the latest generation. In giving freedom to the slave we assure freedom to the free — honorable alike in what we give and what we preserve.”

Most post-Civil War presidents used the message hoping to soothe congressional tensions. Theodore Roosevelt, however, used his annual messages as written extensions of his “bully pulpit” approach to the presidency. Given his love for speeches and his flair for the dramatic, it is surprising that Theodore Roosevelt did not renew the tradition of presenting the message to Congress in person and in his own voice.

The address became a speech again two presidents later. On April 8, 1913, President Woodrow Wilson delivered a State of the Union speech to Congress. Whereas Jefferson preferred the image of president as one of an office rather than a personality making suggestions to Congress, Wilson wanted to remind Congress that the president was an individual person.

“I am very glad indeed to have this opportunity to address the two Houses directly and to verify for myself the impression that the president of the United States is a person, not a mere department of the government hailing Congress from some isolated island of jealous power, sending messages, not speaking naturally and with his own voice — that he is a human being trying to cooperate with other human beings in a common service,” Wilson said.

As radio then television became mainstays of American life, Wilson’s approach made more sense because it allowed presidents an opportunity to present their plans, in their own voices, for not only Congress but directly to the American people.

Presidents following Wilson — Warren Harding, Calvin Coolidge, and Herbert Hoover — gave a sorted mix of the Jefferson and Wilson approaches to the State of the Union. Harding gave two oral messages; Coolidge gave only one, which marked the first radio broadcast of the annual presidential message; Herbert Hoover gave no State of the Union speeches, opting to deliver each of his annual addresses as written messages.

Franklin D. Roosevelt established the spoken State of the Union as a new American tradition, giving 10 out of 12 annual messages as speeches, and broadcast them on radio. FDR is also the president who gave popular rise to the phrase “State of the Union” in calling his speeches the “Annual Message to Congress on the State of the Union.”

President Harry S. Truman gave the first televised State of the Union in 1947, and he is one of three post-FDR presidents to submit a written State of the Union rather than a speech. Truman’s came in 1953, followed by Dwight D. Eisenhower in 1961 and Jimmy Carter in 1981. On each of these occasions, the State of the Union message was a parting shot from presidents leaving office. Most departing presidents do not submit a State of the Union.

In 1956, Eisenhower, recuperating from a heart attack, presented a filmed summary of his State of the Union message. In 1973, Richard Nixon sent a written message, explaining that the State of the Union, as a speech, came too closely after his inauguration speech for his second term.

Other adjustments through the years have affected the way in which the State of the Union will likely be presented tonight. In 1965, President Lyndon B. Johnson changed the speech’s time from early afternoon to the evening so more people could see and hear it on TV. In 1966, network television offered time after the speech for the opposition party to respond to a president’s views. During a State of the Union speech by Ronald Reagan, he introduced “regular Americans” who were invited to attend — a tradition that has been followed by subsequent presidents in almost every State of the Union address since.