Monday's resounding loss at the hands of the Liberals is likely to force the pro-independence party to do some soul searching as it faces the grim possibility that its dream of a sovereign Quebec is on hold for several years.
It also spelled the end of Marois's political career after she announced late Monday night she will step down as party leader.
The defeat means the PQ has headed a Quebec government for only about a year and a half out of the last decade.
Entering the campaign, opinion polls had suggested the minority PQ government was within striking distance of securing a majority mandate.
But that support began to slide after Marois's superstar candidate, Pierre Karl Peladeau, raised his fist in the air and vowed to make Quebec a country — an idea most Quebecers oppose.
Marois, who became the province's first woman premier in 2012, followed up the Quebecor majority owner's dramatic proclamation by musing for days about how a sovereign Quebec would operate.
Looking back, Peladeau's maiden political speech was perhaps too forceful, said PQ supporter Steve Beauchamp.
"Maybe he came on a little too strong when he put his fist in the air — it might have been a bit much," Beauchamp said as he watched the results roll in at the party's headquarters in Montreal.
"Maybe he scared a lot of people."
Beauchamp, 31, said the entrance of Peladeau, one of the most powerful media magnates in Canada, might have been the turning point in the PQ campaign.
The party will have to decide how to proceed now that secession, long its raison d'etre, has proven so hazardous to its political fortunes.
"Yes, certainly we have our answer tonight," said Beauchamp, when asked if sovereignty had become toxic for the PQ. "The people have spoken."
Peladeau, meanwhile, won his seat Monday in Saint-Jerome, north of Montreal.
With his entry into the national assembly, he will likely become a contender to succeed Marois.
Following his victory in Saint-Jerome, Peladeau was asked whether his pro-independence enthusiasm during that inaugural speech may have hurt the PQ.
"Listen, I joined the Parti Quebecois, I joined a sovereigntist party — I am a sovereigntist," said Peladeau, who also laid what could be the groundwork for an eventual leadership run.
"I will make every effort, all my energy to work for economic development. I really believe that in the 21st century Quebec is a nation.
"It must increase its wealth, it must maintain this capacity that are our values and we do it with the solidarity that has accompanied it."
The PQ ranks includes several possible successors who could make a run for the PQ leadership.
Among the other potential candidates are Bernard Drainville, who was the minister in charge of the secularism-charter file, and Jean-Francois Lisee, who served as minister of international relations.
More than 100 PQ supporters who were gathered at Marois's campaign rally in Montreal fell silent after media outlets began to project a convincing Liberal win, mere minutes after polls closed Monday night.
Inside the Old Montreal hotel, small Quebec flags were handed out to the crowd. The mood, however, was sombre and few people bothered waving the fleur-de-lis at all.
Some people consoled each other with hugs and pats on the back. A few in the crowd rubbed their red eyes.
The audience booed loudly when a TV screen showed an image of Liberal Leader Philippe Couillard and announced he had defeated a PQ incumbent.
Security was particularly tight inside and outside the hotel, strengthened following the deadly election-night shooting during Marois's 2012 victory celebration
Police cruisers were parked in front of the building, as well as in a back alley. Bags were searched and attendees had to pass through an airport-style metal detector to access the rally, which was on the 11th floor.
On election night September 2012, gunshots rang out behind the Montreal club that held Marois's election-night rally, killing stagehand Denis Blanchette and wounding his colleague David Courage.
The shooting took place in an alley just metres from Marois.
The attack prompted guards to rush Marois off the stage during her victory celebration and police arrested suspect Richard Henry Bain, who is facing charges of first-degree murder and attempted murder.
After Peladeau's arrival in the campaign, the PQ struggled to gain traction with its controversial-yet-popular secularism charter.
Marois called the snap election last month with her party riding high in the polls, which suggested it was within reach of a majority mandate.
The PQ started to rise in the polls last summer, when Marois received kudos for her quick response and compassion following the deadly Lac-Megantic rail disaster.
She timed the campaign to take advantage of rookie leader Couillard's lack of experience and, more importantly, so she could capitalize on a boost in the popularity of the PQ, thanks to its secularism charter.
Support for the party appeared to reach new heights on the back of the charter, a controversial project introduced last fall that would have banned public employees from wearing overt religious symbols in the workplace.
Polls suggested the values charter, which would have prohibited headwear such as Muslim veils and Jewish kippas, was popular with a majority of Quebecers, even though many citizens thought it would create divisions.
But opinion surveys also suggested that most Quebecers considered issues like immigrant integration to be far from a top electoral priority, well behind more pressing issues like health care, fighting corruption and creating.
The charter also drew outrage. Opponents took to the streets to denounce the idea. Even past PQ premiers Lucien Bouchard and Jacques Parizeau said it went too far.
Peladeau, known to many simply as PKP, was recruited to beef up the PQ's economic credentials.
The party's collapse continued as Marois spent several days musing about how an independent Quebec would operate — complete with talk of open borders with Canada and the continued use of the loonie in Quebec.
It was a surprising strategy, considering how polls have for years suggested that most Quebecers oppose secession from Canada. The PQ has long been forced to walk a fine line on the subject of independence, still a priority for hardcore supporters.
For days, Marois's rivals attacked her on the referendum issue. Journalists peppered her with questions. The party tried to pivot, but to no avail.
Indeed, the shift in strategy led to a telling, headline-grabbing moment when Marois gently — but firmly — pushed Peladeau away from a microphone as she tried to regain control of her campaign's message.
In the final days of the campaign, Marois admitted she had regrets.
Asked Saturday if she could change one aspect of her campaign, she said she likely "wouldn't answer questions about sovereignty, given that the key issue remains the choice of a government, a strong government."
In the final days, as polls suggested her party had slipped behind the Liberals, Marois warned voters that electing a Liberal government would put some of the leftover politicians from the scandal-plagued Charest era back in power.
Marois also tried a last-ditch effort to attract votes by promising at the 11th hour to cut income taxes, a move opponents dismissed as an act of desperation.
The PQ budget that was introduced two weeks before the election call made no mention of tax reductions. Marois said she didn't mention the plan earlier in the campaign because "not a lot of people asked me."
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