Presidents have long invited prominent individuals and average Americans to sit with the first lady during the State of the Union address, often as a way to underscore a theme.
For President Barack Obama's last State of the Union address Tuesday, the high-profile spot in the first lady's box will be notably empty in honor of victims of gun violence "who no longer have a voice."
"Their absence means something to this country," President Barack Obama told grassroots supporters Friday. "They need the rest of us to speak for them. To tell their stories. To honor their memory."
The president said he hopes the empty seat will be a reminder of those who have been killed, and a message to Congress that "it’s their responsibility to do something about this." Obama has accused the gun lobby of taking Congress hostage.
The last intentionally empty chair at the State of the Union was placed behind then-first lady Laura Bush's box during the 2003 address. The White House said it "symbolizes the empty place many Americans will always have at their tables and in their lives because of the attacks on Sept. 11, 2001."
The announcement comes after the president's week-long blitz promoting more regulation of fire arms, which included a tearful proclamation on new executive action, a New York Times op-ed article and a televised town hall meeting. During Friday's conference call with supporters, Obama spoke about "common sense" steps he is taking to address gun violence.
Obama is expected to make the case for tougher gun control laws during his speech Tuesday. The series of proposals, which the administration first unveiled on Tuesday, are designed to close holes in the federal background check system for gun purchases, devote millions of additional dollars to mental health services, and develop smart gun technology.
The White House says Edith Childs of South Carolina and Earl Smith of Austin, Texas, will also attend the State of the Union as the president's guests.
Childs was a councilmember in Greenwood County when she and then-Illinois Sen. Obama met in June 2007. He credits her with coining the "Fired up! Ready to go!" call-and-response that became a rallying cry for his campaigns.
Smith, a Vietnam veteran, was head of security at an Austin hotel when he met Obama in February 2008.
They were in an elevator when Smith gave Obama a military patch he'd worn with an artillery brigade that suffered more than 10,000 casualties. Obama carried the patch with him for the rest of the campaign.
Since taking office in 2003, Obama has had a total of 23 guests sit with the first lady at the State of the Union. They have included a bank president, a single mother and a small business owner.
In 2015, Obama’s invitation to Alan Gross was considered to be a reflection of the thawing of U.S.-Cuban relations. Gross was accused of espionage by a Cuban court and sentenced to 15 years for bringing phones and computer equipment into the country. He was released in Dec. 2014 after serving 5 years in prison.
Sergeant First Class Cory Remsburg was his guest in 2014. Remsburg was almost killed by a roadside bomb in Afghanistan.
In 2013, Obama invited Brian Murphy, a police officer who was first responder to a mass shooting at a Sikh temple in Wisconsin.
The Associated Press and NBC's Rajeev Dhir contributed to this report.