PM Lee paused as he was talking about changes to the elected presidency, and his face contorted before he lost balance.
Many feared that he had suffered a stroke.
However, the Prime Minister’s Office has announced that PM Lee’s heart is fine and that he did not have a stroke.
The PMO said that PM Lee was feeling unsteady because of “prolonged standing, heat and dehydration”.
PM Lee is expected to resume his speech at 10.40pm tonight.
He first spoke in Malay, then Mandarin, before starting his rally speech in English at 8pm.
Viewers were understandably nervous as this comes 3 months after Finance Minister Heng Swee Keat’s collapse during a Cabinet meeting.
Mr Heng suffered a stroke and was rushed to Tan Tock Seng Hospital where doctors performed a surgery on his brain to close an aneurysm.
The operation was performed successfully and Mr Heng has been given time off official duties to recuperate.