"Xi Jinping needs somebody like Jiang Zemin to say that he's doing well and also to project the facade of unity that there is nobody challenging him," said Willy Lam, an expert on party politics at the Chinese University of Hong Kong.
Jiang is foremost among the party's retired elders, who enjoy tremendous clout even though they typically have no official posts. He oversaw a four-fold expansion of the economy, the reversion of Hong Kong from British to Chinese rule, and the country's entry into the World Trade Organization. Jiang stepped down as party leader in 2002, although he led the commission that controls the armed forces for another two years.
And although Jiang is from a different party faction than Xi, he was regarded as his patron in putting him in line more than five years ago to replace Hu. His praise of Xi who took over as party boss last November and as president in March is being interpreted as a bid to show solidarity in the highest echelons of the Communist Party.
Such unity helps bolster Xi's new administration as it tries to undertake promised economic reforms and show that it's cleaning up widespread corruption in party ranks. The government has also had to tackle violent unrest in the ethnic minority region of Xinjiang and massive protests over environmental pollution.
"At this moment, where the ruling Chinese Communist Party's various factions are concerned, they face common difficulties," said Zhang Lifan, a Chinese historian and political analyst. "External and internal pressures are very heavy and domestic contradictions are very acute."
"This could be possibly an emphasis on unity to jointly deal with the challenges to power that may arise," Zhang said.
Zhang also sees the former president's brief resurfacing as a sign of maneuvering for influence among the party elite, and a signal that the factions he and Xi represent have or are trying to find common areas of cooperation.
"Perhaps at the back of this appearance (by Jiang) is that some kind of compromise has been made between the factions," Zhang said.
Jiang's appearance with Kissinger who is a frequent visitor to China could also be another bid by the retired party elder to burnish his credentials.
"Jiang Zemin is a person who refuses to fade into the sunset," Lam said.
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Follow Gillian Wong on Twitter at twitter.com/gillianwong