Jacques Daoust entered provincial politics as part of a triumvirate of economic stars that Philippe Couillard had recruited in the run-up to the 2014 election.

Along with the respected economists Martin Coiteux and Carlos Leitao, the former head of Investissement Québec was supposed to help revive Quebec's economic fortunes.

But just two and a half years into his political career, Daoust announced he was giving up his position as transport minister and leaving politics altogether.

Philippe Couillard introduced his three economic heavyweights Jacques Daoust, Martin Coiteux and Carlos Leitao on the campaign trail in 2014. (Paul Chiasson/CP)

His position in Couillard's government became untenable when a series of emails surfaced between his then chief of staff, Pierre Ouellet, and an executive with Investissement Québec.

​The emails appeared to contradict Daoust's longstanding claim that he didn't give his approval for the sale of shares in Quebec hardware chain Rona to U.S.-based Lowe's while he was economy minister.

Those emails, copies of which were obtained by Radio-Canada, revealed that Ouellet indicated to Investissement Québec that Daoust backed the transaction.

The Parti Québécois held a news conference Friday morning calling Daoust a "liar" and demanding his resignation.

Even in stepping down, though, Daoust denied he ever misled the public about his role in the Rona-Lowe's deal.

"Even though I have done nothing wrong and always told the full truth, the issue about Rona's shares has become a distraction that is casting a shadow over the plans of our government," Daoust said in a statement released late Friday afternoon.

"I therefore contacted the premier to announce that I'm stepping down as deputy for Verdun and as minister of transport, sustainable mobility and transport electrification."

Quebec Premier Philippe Couillard, left, and Quebec Transport Minister Jacques Daoust before a party caucus meeting in April. (Jacques Boissinot/Canadian Press)

An unnecessary scandal

To close observers of Quebec politics, it was an unnecessary scandal that claimed what had once been a promising career.

As minister of the economy, Daoust was responsible for Investissement Québec. But the Rona deal didn't even require ministerial approval.

Opposition parties simply wanted the development agency to use its stake in Rona to protect a Quebec company from a foreign takeover.

"To me, he should have just said if he knew or didn't know, because he couldn't have stopped it anyway," said Yolande James, CBC Montreal's political analyst and former cabinet minister under Jean Charest.

Rona's shareholders, moreover, overwhelmingly backed the deal in a vote in March. A hostile takeover this was not.

Couillard demanded answers

"I think the government, Mr. Couillard, didn't want him to go," James said. "They didn't want to have to face a minister leaving."

Couillard had stood by Daoust through a number of scandals, including evidence his office dragged its heels responding to a report exposing irregularities within the transport ministry.

He had also drawn ire within his own party for tabling reforms to Quebec's taxi industry that were seen as out-of-touch with the popularity of ride-hailing services.

But Couillard's support appeared to evaporate after the emails between Ouellet and an Investissement Québec executive went public.

Earlier today, Couillard said the emails raised "serious questions" that "demanded serious answers."

Couillard had stood by Daoust through a number of other scandals. (Radio-Canada)

Big hole to fill

Transport is considered an important, if volatile, file, and Daoust's departure leaves a big hole for Couillard to fill. The premier is scheduled to announce a cabinet shuffle at 10 a.m. on Saturday.

Daoust's successor will take over a ministry that is in disarray. Transport ministry insiders have described a workplace culture beset by intimidation and allegations of collusion.

And then there's also the thankless task of managing the frustrations of Montreal commuters. Daoust had just warned Montrealers that traffic in the city will reach new lows thanks to a spate of road projects.

Perhaps because of that turmoil, Transports Quebec has eaten through several ministers in recent years. Daoust was the fifth since 2010.

The association of Quebec's bitumen producers released a statement Friday evening, decrying the "lack of stability and continuity at Transports Quebec."