![Benazir Bhutto campaigning in Rawalpindi, Pakistan - 27 December 2007](/5649607756495938.jpg)
Bilawal Bhutto Zardari is addressing many thousands of Pakistan People's Party (PPP) supporters gathered near his family's shrine in Sindh province.
Mr Bhutto Zardari, whose father is President Asif Ali Zardari, has so far kept a low profile as PPP chairman.
Ms Bhutto died in a gun and bomb attack during her 2007 election campaign.
In remarks carried by Pakistan state television, Mr Bhutto Zardari said the people were "the source of power".
"Benazir sacrificed her life to uphold democracy," he said. "The beacon of democracy continue to shine."
The 24-year-old Oxford graduate has been PPP chairman since his mother's assassination by Taliban militants. He cannot contest an election until his 25th birthday.
Show of strengthSecurity was tight as activists carrying portraits of Ms Bhutto and her father, former Prime Minister Zulfiqar Ali Bhutto, gathered at the family's shrine in the city of Larkana.
Mr Bhutto Zardari was expected to use the occasion to articulate his vision for the party, says the BBC's Shahzeb Jillani.
With parliamentary elections set to be held in 2013, the governing PPP is keen to use the rally as a show of strength to demonstrate that despite widespread criticism over its performance during the past five years, it still enjoys popular support, our correspondent says.
![Bilawal Bhutto-Zadari](/64950171zardariap.jpg)
Mr Bhutto Zardari's father, President Zardari, has been at the forefront of the party until now but faces dwindling support over corruption allegations.
Those fed up with President Zardari's politics are looking to his son to help revive the party's mass appeal, our correspondent says.
The Bhutto dynasty has been a major political force since Pakistan gained independence in 1947.
Ms Bhutto, whose father founded the PPP, was prime minister from 1988 to 1990 and from 1993 to 1996.
On both occasions she was dismissed from office for alleged corruption.
No-one has been charged with her assassination.
A UN inquiry in 2010 found that her murder could have been prevented and that the subsequent investigation was bungled.