Patrick Brown's Progressive Conservatives are sitting on a swollen war chest after a year of blockbuster fundraising, and the party's membership rolls have expanded to record levels. Trouble, however, is brewing inside Ontario's Official Opposition.

A provincial election is due next spring, and Ontario's PC Party is far ahead in most polls. But as the Liberals face high-profile trials that will keep past problems in the spotlight, the Tories struggle with their own turmoil. Several local nomination races have descended into chaos, leading to mass resignations and lawsuits.

Would-be nominees and local party officials in as many as 14 ridings across Ontario have complained about voter fraud and broken rules at nominations, or ballot-box stuffing. Some candidates in nomination races have alleged in lawsuits that the party's president was at some of the contentious votes and ignored their concerns.

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Mr. Brown, who has been the party's leader since 2015, hired auditors from PricewaterhouseCoopers in May to monitor future nomination meetings after a number of local battles were marred by allegations of fraud. At the time, Mr. Brown said he chose to add the extra oversight because the party's contests were "more energized" than in past years. He also approved all 64 candidates nominated to that point, including those in races that were dogged by allegations of fraudulent votes. Despite the auditors, problems are still being raised at nominations.

A request to the PC Party and Mr. Brown for comment about the number of nomination issues over the past year was forwarded to party president Rick Dykstra. He declined an interview, but responded by e-mail. "Within the last year, our party has experienced unprecedented enthusiasm and participation in our nomination process. Competition is good for our party and we have seen a lot of it, unlike the lack of interest in Liberal Party nominations," he wrote in a statement.

"I have only heard excitement about the upcoming campaign," he added.

A number of PC Party members have resigned over the past year, including senior leaders and the heads of local riding associations, citing the hard-fought nomination battles and what they perceive as Mr. Brown's failure to respond to allegations.

"There are a lot of shady things going on here and I don't like it," Marilyn Mushinski, a cabinet minister when Mike Harris was PC premier, told The Globe and Mail in late June. Only days earlier, on June 26, police were called to a nomination contest for the riding of Scarborough Centre. According to Ms. Mushinski, there was chaos after a last-minute change of venue, voting lines snaking around ballot boxes, and ballots appearing out of nowhere as the lights were flicked off and on.

"I have never in my nearly 40 years of being in politics have ever come across something like this. It's an affront to grassroots democracy," said Ms. Mushinski, the most recent Tory elected to represent the crucial riding in Toronto's suburbs. At the time, she told The Globe she believed Mr. Brown's office orchestrated the mayhem to get its favoured candidate elected. Most of the Scarborough-Centre Progressive Conservative association riding board resigned in late August and early September, citing a lack of confidence in Mr. Brown.

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Contacted again by The Globe in August, Ms. Mushinski was one of several party members and unsuccessful candidates for nominations who said their lawyers had instructed them not to speak publicly about the party any more. Some of the candidates said they were facing the threat of lawsuits if they spoke publicly. Mr. Dykstra would not comment, citing continuing legal proceedings.

After a May 7 nomination meeting in the riding of Hamilton West-Ancaster-Dundas, two candidates complained to the party alleging ballot-box stuffing. Vikram Singh, who lost the race to 25-year-old Ben Levitt, a staffer for federal MP David Sweet, filed for a judicial review of the race's outcome citing irregularities. In response, Mr. Dykstra swore an affidavit in which he dismissed Mr. Singh's complaint. According to the party president, the nominations are only a guide to Mr. Brown's choice of candidate; he can reject a locally elected person based on his instinct and appoint someone else, he said.

"The nomination meeting is not determinative of who will ultimately be listed on the ballot as a PC party candidate in the general election," he said in the affidavit.

By next June, the deadline for when an election must be called, Ontario's Liberal Party will have held power for nearly 15 years. On paper, Mr. Brown's Tories are the best bet to end Premier Kathleen Wynne's time in office. While the Tories are untested after years in opposition, they are flush with cash.

Ms. Wynne's approval rating is flirting with single digits, and a fundraising effort in 2016 raised only $6.5-million to the PCs' $16.1-million. Beset by high energy prices that have soured the public mood, Ms. Wynne's government is in the public eye as two trials unfold this fall, one in Sudbury, where former Liberals face bribery charges, and a criminal case against former Liberal staffers over the alleged deletion of documents connected to the cancellation of gas plants.

While Mr. Brown prepares for next year's campaign, some of his choices have divided his conservative base of support, most notably his backing for carbon pricing and sex education in the province's schools. Further divisions have become raw at heated nomination races.

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There has been anger over races in King-Vaughan, Mississauga-Erin Mills, Durham and Milton. A six-page letter outlined the problems at a vote in the riding of Burlington and unsuccessfully called for a second vote. Two candidates in Flamborough-Glanbrook were told the riding was being kept for a local councillor. The local party executives in the ridings of Kanata-Carleton, Newmarket-Aurora and Ottawa West-Nepean have resigned over the past year, alleging vote impropriety or a "toxic environment" in the party. At least two lawsuits have emerged from the contested nomination battle in Hamilton West-Ancaster-Dundas.

The number of nomination issues is higher than normal, said Henry Jacek, a political science professor at McMaster University. While some of the tensions might stem from candidates looking to ride a Tory victory wave into Queen's Park in 2018, it also shows that Mr. Brown, who was a federal MP before winning the leadership, still lacks familiarity with his party. "They have a brand new leader who doesn't seem to have as much control over the party, unlike someone who was premier or who has a long history in the party. I can't imagine any of this happening when Tim Hudak was leader," he said, referring to Mr. Brown's predecessor.

Leslie Noble, a senior staffer under Mr. Harris who remains influential in the party, said the nomination issues are not unique to the Tories. "There are problems all across," she said. "It's par for the course in politics, it's the way it goes."