Their 11th hour show of solidarity — shot through with equal measures of moral indignation and desperation — came just hours before Harper was to depart for China, where he is to advance an economic agenda and meet China's top political leaders.
They were speaking Wednesday on Parliament Hill on behalf of Wang Bingzhang, the founder of the overseas, pro-democracy movement in China. Wang has been in a Beijing prison since 2002, serving a life sentence in solitary confinement for trying to foster democracy in China from abroad.
Wang received a doctorate at Montreal's McGill University and many of his relatives are Canadian.
"I ask Prime Minister Harper to seize all diplomatic opportunities with China to seek the release of my father," said his daughter, Ti-Anna Wang, of Montreal, who's been barred from China for the past five years because of her activism.
"I believe high-level diplomacy is his best chance at freedom."
Wang was one of the first Chinese to study abroad a generation ago. His exposure to democracy inspired him to found China's overseas democracy movement.
Chinese agents abducted him in Vietnam in 2002 and took him to China, where he was sentenced to life after what his daughter called "a sham trial."
Ti-Anna Wang said she wished Harper would meet her family personally so he'd have a better appreciation of China's human rights abuses.
"I want our stories and efforts to be heard, acknowledged and taken into serious consideration when Canada devises its foreign policy with China," said the 24-year-old.
"It was the very values espoused by Canada and other democracies that inspired my father. If we cannot turn to this government and its leaders to advocate for his release, to whom else can we turn?"
The prisoner's brother, Wang Binjgwu of Toronto, who has maintained a seven-day vigil on and around Parliament Hill, said his brother's mental and physical health is declining.
In last meeting with his brother in prison last February, he found his brother had lost weight and had written a letter to family that "doesn't make sense."
During his incarceration, Wang has suffered three strokes, said his brother.
"Mr. Harper, please save my brother," Wang said at a Centre Block news conference. "I'm here to have this heartfelt, desperate plea for our prime minister to personally raise the case with the Chinese officials."
Conservative MP Scott Reid said he's discussed Wang's case with Harper, but he wouldn't provide details of what could be done, citing the need to keep a conversation with his prime minister private.
"The fact that these issues should be communicated on an ongoing basis, and at every possible opportunity, is a given," he said.
Liberal MP Irwin Cotler, a human rights lawyer who has made a career out of fighting for political prisoners, said he's discussed Wang's case with Foreign Affairs Minister John Baird, and "respects his commitments."
Baird is one of several cabinet ministers accompanying Harper to China.
The Canadian delegation arrives in Beijing on the weekend after a visit to the industrial centre of Hangzhou. Harper is to meet Chinese President Xi Jinping, who has called for a more open form of government since taking power in late 2012.
Cotler said Harper should press Xi to live up to his rhetoric, suggesting that anything short of that could be seen as an insult to Canada.
"We, Canada, as country, as a people, and a government, as a Parliament, have a compelling responsibility to raise this case and cause," Cotler said.
New Democrat MP Wayne Marston and Green party Leader Elizabeth May joined Reid and Cotler in calling for Wang's release.
Harper's office has said it will raise human rights but has not specifically mentioned Wang's case.
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