Reagan was holding Rubio's arm as they walked in the room together.
Then gasps erupted from the room as the 90-year-old lost her footing.
Rubio grabbed her arm and caught her right before she hit the floor.
The audience gave a standing ovation and applauded the first lady as she rose.
Reagan asked Rubio to speak at her husband's presidential library in California following his election to the Senate.
For more stories from WTVT in Tampa Bay go to myfoxtampabay.com