Bertschi, a father of six who ran unsuccessfully for the party in 2011 in Ottawa-Orleans, is a relative unknown.
He's going up against prohibitive favourite Justin Trudeau, eldest son of former prime minister Pierre Trudeau and the party's undisputed rock star.
Bertschi is casting himself as the underdog champion of grassroots Liberals, in contrast to Trudeau, whom he depicts as the manufactured choice of Liberal elites.
Two other relative unknowns — Toronto lawyer Deborah Coyne, mother of Trudeau's half-sister, and Vancouver Crown prosecutor Alex Burton — have also officially launched campaigns.
But Bertschi insists Liberals have only two real choices in the leadership race, which culminates April 14.
"We can choose to continue down the same old path of manufactured leadership from the backrooms, where we are led with top-down directives, where the grassroots are ignored and where our party is controlled by a handful of elites," he said in a speech Wednesday evening to supporters in Orleans, the text of which was made available earlier.
"Or we can choose leadership that is committed to rebuilding the Liberal party from the grassroots, where your voice and the voices of Canadians are listened to and respected."
A number of other long-shots are poised to take the plunge, including Toronto lawyer George Takach and Ontario government economist Jonathan Mousley.
Former MPs Martha Hall Findlay and Martin Cauchon are still weighing their chances.
Many Liberals are hoping the race will not turn into a Trudeau coronation. But with one Liberal luminary after another taking a pass, the best hope for a serious challenger likely lies with Montreal MP Marc Garneau.
Garneau, Canada's first astronaut and the Liberals' House leader, is expected to take the plunge as early as next week.
The stiff $75,000-entry fee set by the party — due in three instalments by mid-January — may yet prove an insurmountable obstacle to some of the dark horse contenders.