The PQ expressed concern about media reports that an influx of English-speakers and other non-francophones from outside the province were trying to vote in the April 7 election.
By late afternoon, however, the province's chief electoral officer brought forward numbers showing there were no signs of an irregular increase in voter registration.
"The abnormally high number of requests doesn't exist," said spokesman Denis Dion.
Still, the PQ's strong language meant the controversy dominated Day 19 of the campaign.
One PQ candidate at the news conference, justice minister Bertrand St-Arnaud, called on the province's chief electoral officer to closely examine new attempts to register to vote.
"We don't want this election stolen by people from Ontario and the rest of Canada," St-Arnaud said in Montreal.
Another party candidate, former student leader Leo Bureau-Blouin, added he wants to make sure the election is decided by Quebecers.
"We are concerned by the fact that many, many people who are not registered on the list want to be registered," said Bureau-Blouin, who in the past has made increasing voter participation among youth a priority.
PQ Leader Pauline Marois raised her own concerns later in the day.
There have been numerous media reports lately of English-speaking university students trying to register to vote. Some students complained they were turned away even though they believed they had the necessary documentation.
While Quebec's English-language media has generally focused on those cases, French-language counterparts have sometimes presented the issue differently — as an effort by students from outside Quebec to influence the outcome of the election.
The PQ's St-Arnaud said he found a report in Sunday's Le Journal de Montreal particularly troubling. It described an attempt by "hundreds of Ontario students" to vote against PQ leader Pauline Marois.
The parent company of Le Journal de Montreal, Quebecor, was founded by the family of Pierre Karl Peladeau, a star candidate who is running for the PQ in the election.
Peladeau stepped aside as Quebecor’s CEO last year and when he announced his candidacy this month he said he would place his ownership stake in the company in a blind trust and insisted his media outlets would maintain independent coverage.
The story from Le Journal de Montreal story came after Mathieu Vandal, the head of the election revision board for a downtown Montreal riding, resigned on Friday and went public with concerns that an increased number of non-francophones were attempting to register and weren't being adequately screened.
Dion said there had been an increase in attempts by out-of-province students to register in some ridings, but that Vandal's comments were "alarmist" and had "exaggerated" the situation.
He said the issue was further complicated because some officials didn't understand the registration rules.
That may be why a number of English-speaking students have come forward to complain they were unfairly denied the right to vote.
In one case, a McGill PhD student said he was turned away even though he has lived here since 2008 and only takes three weeks vacation a year from his lab work.
Sean Beatty, a 31-year-old from British Columbia, was so frustrated he secretly recorded an exchange with elections officials and post it online, where it quickly made the rounds on social media.
Beatty said he has voted previously in a federal election in Quebec, and was compelled to register in the provincial election this time because he disagrees with the PQ's proposed charter of values.
"I'm really disturbed by the way the process is set up, the idea that someone can deny you the right to vote without requesting any additional documentation or having an appeal process," Beatty said in an interview.
Beatty said he presented his passport and utility bills and that he has previously filed taxes in Quebec, though he has still has a British Columbia health card.
To register in Quebec, Dion said a voter must be a Canadian citizen and have lived in Quebec for six months. They must also have the intention of making Quebec their home, a term that's open to interpretation.
Dion said officials also take into account other evidence, such as proof of a bank account in a Quebec institution, a Quebec health insurance card or driver's licence, or a Quebec income tax return.
The PQ's strong stance on the voting controversy recalled complaints in the aftermath of the failed 1995 referendum, when federalists were accused of taking unfair measures to boost the Yes vote.
Rival parties have so far avoided talking up the controversy. Liberal Leader Philippe Couillard and Francois Legault, head of the Coalition party, both said they would leave the issue up to the chief electoral officer.
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