Stephen Harper's Conservative Party has quietly nominated more than 100 candidates for the 2015 election, sources say, in a low-key process that has produced only a handful of races within the party.

The figure amounts to roughly one-third of the Conservatives' slate in Canada's 338 ridings. The NDP has yet to nominate any candidates while the Liberals expect to nominate roughly 80 by July 1.

The Conservatives announce nomination races only to members in a particular riding, typically through a hard-copy letter. Victorious nominees are not publicly announced.

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At least 30 incumbent Tories who were acclaimed as candidates without a vote have since made their own announcements, while other nominees appear to have stayed quiet so far.

Incumbents are often seen as unbeatable and prospective candidates may instead target ridings without a Tory incumbent. However, several would-be challengers of the incumbent MPs have already had their papers rejected by the party, allowing certain incumbents to be acclaimed without a race. All told, the party has only four races brewing thus far.

The four include Eve Adams, Rob Anders, Mike Lake and David Tilson. Mr. Anders has already lost his nomination, while votes have been scheduled for Ms. Adams and Mr. Tilson later this month.

The Conservatives declined to say which ridings were already complete. "We're running fair and open nominations across Canada, and will have candidates in place in time for the next election," party spokesman Cory Hann said.

At least one of the 35 incumbent Liberal MPs has already faced a nomination vote – former leader Stéphane Dion, who won – while others have been acclaimed. Liberal national director Jeremy Broadhurst declined to say how many nominations have been done so far, but said roughly one-quarter of the 338 ridings will be wrapped up by summer, including the bulk of the incumbent MPs, with another blitz expected in the fall.

"That's pretty much where we wanted to be," Mr. Broadhurst said. The Liberals say they've had 800 requests for nomination forms countrywide so far, including certain Quebec ridings where the party expects five- or six-way races. "There's lots of interest out there," Mr. Broadhurst added.

Both the Conservatives and Liberals have pledged open nomination races only to face complaints within party ranks about interference with the process. That includes the case of Ms. Adams – her fiancé, former Conservative Party executive director Dimitri Soudas, was forced out of his job after questions about his role in her race. Liberal Leader Justin Trudeau, meanwhile, is being sued for interfering in a Toronto nomination race and last week blocked new anti-abortion candidates from seeking any nomination.

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The NDP, with 99 MPs, have argued they're the only party running truly open nominations, which are largely up to local electoral district associations.

"A genuinely open and member-driven process takes time. We've opened nominations in about half the country and, while we centrally co-ordinate, it's the NDP members and their local electoral district associations who are undertaking the work of recruiting candidates and organizing nomination meetings," NDP spokesman George Soule said Tuesday.