Ontario Premier Kathleen Wynne will call five by-elections at once in a major test of her leadership this summer. The writs will be formally dropped Wednesday, government sources told The Globe and Mail, with an election date of Aug. 1.

And the Liberals are wheeling out the big guns in a bid to hold on to the two Toronto seats up for grabs, nominating city councillor Peter Milczyn, a member of Mayor Rob Ford's executive, in Etobicoke Lakeshore and Mitzie Hunter, CEO of city-building organization CivicAction, in Scarborough Guildwood, on Tuesday.

The by-elections will fall in the height of summer – an unusual time for a vote – on a Thursday before a long weekend.

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Mr. Milczyn does not plan to give up his council seat to run, noting that regular meetings at city hall will soon stop for the summer. Mr. Milczyn, an architect who chairs the city's planning committee, said the jump to provincial politics was unexpected.

"Over the course of the last week I was approached by a number of people – insistently so. It's an opportunity to move ahead," he said. He framed the impending move to Queen's Park as a chance to work on transportation and planning issues on a larger scale.

The Progressive Conservatives have nominated Steve Ryan, a Toronto police detective in the force's homicide squad, in the riding.

The seat was previously held by Laurel Broten, a former education minister who became a lightning rod for teachers last fall when she imposed contracts on them.

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Ms. Hunter, meanwhile, is set to get the nod in Scarborough Guildwood. The largely working-class constituency became empty last week when former cabinet minister Margarett Best resigned from the legislature.

A prominent advocate for expanded public transit, Ms. Hunter's priorities are certain to jibe with those of Ms. Wynne, who is pushing a massive, $50-billion plan to build new subways and light rail lines.

Ms. Hunter also pointed to the government's job-creation plans and housing policies as planks in her platform.

"I really believe that Kathleen Wynne has put forward the issues that are really important -- employment opportunities, housing, transportation," she said. "Employment is really important, for young people but also for everyone, the economy is critical and transportation is something that is really important for residents that need to get to work."

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Ms. Hunter will take a leave of absence from the CivicAction to campaign.

The Tories have nominated Ken Kirupa, a Sri Lanka-born real-estate agent and entrepreneur, in the riding.

The New Democrats have not yet nominated a candidate in either riding, but are planning to do so within the week.

The NDP is in a stronger position in Windsor Tecumseh, where the party has nominated Percy Hatfield, a city councillor and former CBC journalist. He will square off against Liberal real-estate agent Jeewan Gill and engineer Robert de Verteuil, who is running for the Tories. The seat, vacated by former finance minister Dwight Duncan earlier this year, is prime territory for the NDP, sitting in the middle of the province's manufacturing belt. The New Democrats already hold the riding federally and have a strong organization in the city.

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London West, meanwhile, is shaping up to be a tight, three-way tussle. The Liberals have recruited former Ontario Secondary School Teachers' Federation president Ken Coran, who will go toe-to-toe with lawyer Ali Chahbar of the Progressive Conservatives and Peggy Sattler, a former school board chair who will carry the NDP's banner.

Mr. Coran's nomination raised eyebrows: mere months ago, he lead his union in a battle against Ms. Broten's since-repealed legislation and helped defeat the Liberals in a previous by-election in Kitchener-Waterloo.

Across the province, in Ottawa South, voters will be electing a replacement for former premier Dalton McGuinty, who gave up the seat last month after representing it for 23 years. Mr. McGuinty's constituency assistant, John Fraser, will run for the Liberals against Tory businessman Matt Young. The NDP have not yet nominated a candidate.

The Tories accused the Liberals of playing "dirty pool" by scheduling the elections at a time when people will be more concerned with barbecues and holidays than politics.

"It's regrettable that Kathleen Wynne would try to pull the wool over the public's eyes by having a vote on the eve of a long weekend," said PC MPP Lisa MacLeod. "I think that's dirty pool and I think people will see right through it."

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The PCs have already been campaigning hard, nominating candidates in nearly all of the province's ridings months ago and running attack ads against Ms. Wynne on prime time television.

But Ms. MacLeod tried to set her party's expectations low.

"These are long-time Lib seats, all five of them … they do have the infrastructure in place in these seats, so it's going to be an uphill battle for us and the NDP in all of them," she said.

The New Democrats, however, were far more optimistic Tuesday. MPP Cheri DiNovo said voters have been pleased with her party's ability to wring concessions – including a cut to auto-insurance premiums and youth job-creation programs – from the government and that the NDP had a good shot at picking up votes.

"We think we're going to do very well," she said. "We've held the government to account, we've achieved a great deal for the folk who live in this province and we look forward to good news."