In launching his campaign Friday to an audience of about 100 people, Cauchon paid tribute to the now-defunct long gun registry and proposed a more active federal role in shaping medicare.
The former Jean Chretien cabinet minister lauded the old government's record, which included rejecting bank mergers and accepting same-sex marriage, the latter being a policy Cauchon personally advanced when he was justice minister.
He spoke of restoring Canada's peacemaking image abroad and, closer to home, suggested the federal government should re-engage itself in shaping medicare policy.
"(Health care) is at the heart of Canadians' preoccupations. However, politicians avoid the issue like the plague," Cauchon said in his speech in Montreal.
"The Canadian government must act as a catalyst to spark a discussion aimed at improving and strengthening our public health system."
Cauchon offered a broader message aimed at all left-leaning voters: he called the Liberal party the "true progressive alternative" to the Harper government.
Some of his chief opponents have been casting themselves as centrist pragmatists.
The 50-year-old lawyer said he expects to win a race that also includes presumed front-runner Justin Trudeau and Montreal MP Marc Garneau.
Cauchon, who entered the contest just hours before Sunday's midnight deadline, intends to reach out to Canadians by campaigning full time over the coming months.
He team also has plans to have bigger presence on social media, including Twitter. One reporter pointed out to Cauchon that he has just over 1,100 Twitter followers, compared to Trudeau's 180,000.
"It doesn't mean that those who are following Justin Trudeau, Marc Garneau or any other people in the race — that those people would necessarily vote for that person," Cauchon replied in a post-speech scrum with journalists.
When asked about whether he has support of his former boss — Chretien — he let out a nervous laugh and said he expected he would have to field that question.
"The best guy to talk to is Jean Chretien, ask him," he said, before being asked if he would like to have the former prime minister's public support.
"If you would ask the question to any of the nine candidates around the table, they're all going to say the same (thing): yes, of course."
Cauchon was the final candidate to join the contest, which features a total of nine hopefuls. He retired from politics in 2004 and lost a 2011 attempt to win back his old Montreal riding from Tom Mulcair, now NDP leader.
Cauchon was first elected to the Outremont riding in 1993.
Unlike the other candidates, Cauchon has extensive experience in the federal cabinet. He was the activist minister of justice who paved the way for same-sex marriage and who attempted to decriminalize marijuana use.
Cauchon cited that experience as an advantage in his speech.
"Some people will cast me as the underdog," he said.
"But I believe that my experience in government has been invaluable in helping me to make the tough decisions that will be necessary.
"They'll say I have been out of politics too long, but I believe that my time spent in the private sector has made me more qualified for the job of Liberal leader."
The crowd, which broke into chants of "Martin, Martin, Martin" a few times during Cauchon's appearance, didn't feature any prominent MPs past or present.
But one notable attendee, a former CEO and president of Air Canada, said Cauchon's government experience is a major reason why he's supporting him — even though Garneau is a personal friend.
Pierre Jeanniot believes Cauchon, whom he also considers a friend, can lead the Liberals back to power.
"Of all the people, this guy (Cauchon) has the capability of pulling it through, of doing it, of actually achieving it," Jeanniot said after the speech.
"I think he's someone who has a good vision for the country."
In his address, Cauchon said the federal government's "No. 1 priority" should be raising the living standard of all Canadians, and ensuring the long-term strength and sustainability of social programs.
He also said Canada should develop more foreign markets; restore its international image as a "peace ambassador"; and renew the fight against climate change.
As for medicare, he said his campaign website would invite Canadians to share their ideas for improving the system.
Cauchon's prepared speech added: "On this front, the Conservatives of Stephen Harper have completely abdicated their responsibility." He did not utter this line while delivering the address.
Cauchon acknowledged, however, that under the Constitution the responsibility for health care ultimately falls to the provinces.
On the gun registry, he lauded it as a law-enforcement tool and he criticized the Tories for blocking Quebec's attempts to save data for that province.
In a subsequent exchange with The Canadian Press, Cauchon said he would attempt to revive the registry if he could.
Barring that, he said he would introduce another gun-control measure with a similar purpose.
"Of course we're going to have to think about the question of price, but we need to be able to bring back a tool that will offer exactly the same safety we used to have with the registry," Cauchon said.
"If we can bring back the registry, it'd be great."