And then there were six.

The Ontario Liberals are losing an MPP and the legislature is bidding adieu its most celebrated constitutional scholar.

Nathalie Des Rosiers, a Harvard-educated law school dean and co-author of The Oxford Handbook of the Canadian Constitution, officially resigned as Ottawa-Vanier MPP on Wednesday.

Des Dosiers, a former cabinet minister in premier Kathleen Wynne’s government and one of just seven Liberals to survive the June 2018 election defeat at the hands of Doug Ford’s Progressive Conservatives, left to become principal of Massey College at the University of Toronto.

“It is with a heavy heart that I resign my seat. This decision was never an easy one to take and has weighed on me throughout the summer as I continued to work with the residents of my wonderful riding, Ottawa-Vanier,” she said.

The former University of Ottawa law school dean thanked both her colleagues in the Liberal caucus and “the Independent group,” a reference to the rump that includes Green Party Leader Mike Schreiner and ex-Tory MPPs Randy Hillier, Amanda Simard, and Jim Wilson, who now sit as Independents.

“It has been a pleasure working for you to secure our ability to represent our constituents and have our voices heard at the legislative assembly. Keep up the good work,” Des Rosiers, who was first elected in a 2016 byelection, told them.

“Ontario’s democracy requires nurturing and respect, a duty that belongs to all of us. Let’s never squander it.”

Interim Liberal leader John Fraser said Des Rosiers, former general counsel for the Canadian Civil Liberties Association, “championed important issues like protecting civil liberties and human rights, ensuring environmental sustainability, fighting for pay equity and advocating for the Franco-Ontarian community, to name a few.”

“Nathalie’s well-researched, articulate arguments and clear communication in the legislature were respected by members of all parties. She has been an invaluable member of our team,” said Fraser.

By law, the premier has until next Jan. 31 to call a byelection in Ottawa-Vanier.

But Des Rosiers may not be the only Liberal MPP to be leaving Queen’s Park this summer.

MPP Marie-France Lalonde (Orléans) is seeking the Liberal nomination in her home riding for the Oct. 21 federal election.

Prime Minister Justin Trudeau’s Liberals have yet to set a date to select an Orléans candidate.

If Lalonde, who was also a cabinet minister in Wynne’s government, gets the federal nod she will resign her provincial seat.

Both she and Des Rosiers had considered running for the provincial Liberal leadership, which will be decided March 7.

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Under Wynne and her predecessor, Dalton McGuinty, the Liberals were in power for nearly 15 years until Ford’s Tories trounced them almost 14 months ago.

In the 124-member house, there are 73 Conservative MPPs — including Speaker Ted Arnott, who does not caucus with the governing party — 40 New Democrats, the six Liberals, the three former Tories who now sit as Independents, and one Green.

Robert Benzie is the Star’s Queen’s Park bureau chief and a reporter covering Ontario politics. Follow him on Twitter: @robertbenzie

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