By Bennett Roth, CQ Staff

Lawmakers will arrive early in hopes of grabbing center-aisle seats, and a Cabinet member will be left behind for security reasons.

But President Obama’s speech Tuesday night to a joint session of Congress will not be a formal State of the Union address, the annual speech presidents deliver to satisfy their constitutional requirement to periodically update the legislative branch on national affairs. New presidents have traditionally offered a first speech without the official billing.

The major difference between a State of the Union address and a first-year report is the scope of the speech, said House historian Robert V. Remini. A State of the Union is expected to cover both domestic and foreign matters.

Remini said Obama could, for example, skip a discussion about Afghanistan on Tuesday night. “In a State of the Union he would be obliged to do it,” he said.

From a protocol standpoint, there is no difference between a State of the Union address and a new president’s first speech to a joint session, according to House Deputy Sergeant-at-Arms Kerri Hanley. She said the invitation list is the same and includes the Cabinet, Supreme Court justices, the diplomatic corps and the Joint Chiefs of Staff.

Some lawmakers are known for nabbing aisle seats in the chamber hours before the speech, and Hanley said she expects the “usual suspects” to position themselves to greet the president as he is escorted in. Reps. Eliot L. Engel , D-N.Y., and Sheila Jackson Lee , D-Texas, have often been among those maneuvering to grab spots early.

The Constitution says the president “shall from time to time give to Congress information of the State of the Union.” Presidents George Washington and John Adams addressed Congress, but Thomas Jefferson shunned the practice, contending it was too much like the British monarch going before Parliament. It wasn’t until the 20th century that Woodrow Wilson resumed the practice of appearing before Congress.

After Wilson opted in 1913 to use his first months in office to address Congress on a series of issues including tariffs, a number of presidents have chosen to make their way to Capitol Hill early in their tenure.

One exception was Franklin D. Roosevelt, who didn’t speak before a joint session until more than a year after his election.

Past presidents varied their topics in their first-year addresses. Jimmy Carter emphasized energy while Ronald Reagan, Bill Clinton, and George W. Bush spoke about the economy. Richard Nixon did not address a joint session of Congress early in his term, and Herbert Hoover never spoke before lawmakers, said Senate historian Don Ritchie: “He didn’t put a lot of stock in public speaking.”