OTTAWA - Three federal byelections Monday won't alter the balance of power in Canada's minority Parliament -- not that you'd know it from the frenetic, no-holds-barred campaigning that's preceded them.

Name-calling, mudslinging, allegations of dirty tricks, party leaders traipsing regularly into the two ridings in Manitoba and one in Ontario that are up for grabs.

The five-week contests have been so nasty that the venom regularly spilled over into the House of Commons, forcing Speaker Peter Milliken last week to finally step in and shut it down.

It's a measure of what's at stake -- particularly in the northern Toronto riding of Vaughan -- as federal leaders prepare for a national election widely expected after the next budget in February or March.

For Prime Minister Stephen Harper, Vaughan represents a chance to snatch away a riding held by the Liberals for 22 years, establishing an important Conservative beach head in the last remaining Grit fortress in the country, Toronto.

Just as important, it's an opportunity to sap Liberal morale and destabilize Michael Ignatieff's leadership.

"I think Liberals would be very, very upset," says a Tory insider. "Their morale would be destroyed if we take Vaughan."

Indeed, Tories are privately hoping Vaughan will be for Ignatieff what Outremont was for his predecessor, Stephane Dion. The loss of Outremont, a longtime Liberal bastion in Montreal, in a 2007 byelection triggered an ugly bout of internecine warfare that weakened Dion's already shaky grasp on the reins of his party, which went on to its worst electoral defeat in history the following year.

Harper has left nothing to chance. He recruited former Ontario Provincial Police commissioner Julian Fantino to run for the Conservatives -- a prize catch in a riding with a large Italian constituency. Prime ministers typically don't get involved in byelections but in this case Harper turned up at the start of the campaign to show off his star recruit.

Conservative party spokesman Fred Lorey describes Vaughan as a "steep, steep hill" for the Tories, pointing out that it was among the top 25 best-performing ridings for the Liberals in the 2008 election.

Still, Liberal support in the riding has steadily eroded over the last few elections and the Tories have already picked off three of seven adjacent ridings. When veteran Liberal MP Maurizio Bevilacqua stepped down to make a successful run for Vaughan's mayoralty, the riding was ripe for the picking.

Liberal insiders concede if Vaughan falls it bodes ill for other Toronto MPs who hung on by fewer than 3,000 votes last time, including Ken Dryden, Joe Volpe, Ruby Dhalla, Paul Szabo and Andrew Kania.

Losing Vaughan would undoubtedly trigger another bout of grumbling about Ignatieff, who's already under fire from some Liberal MPs over his support for extending Canada's military mission in Afghanistan. And it could embolden some Liberals to vote Tuesday, in open defiance of their leader, for a Bloc Quebecois motion condemning the extension.

Still, Vaughan is not likely to be Ignatieff's Waterloo, or even his Outremont.

When Dion lost Outremont, most Liberals believed they'd do better with Ignatieff at the helm and some weren't shy about trying to accelerate the succession.

Now, for the first time in decades, there is no leader-in-waiting that disgruntled Liberals seem prepared to rally around. The hard reality that Ignatieff will be leading them in the next election may enforce some discipline on his caucus, if only out of self-preservation

As one insider puts it: "They may not love (Ignatieff) in the party but they're stuck with him."

Moreover, unlike Outremont, the Liberal campaign in Vaughan has not been a shambles. To the contrary, party organizers have poured into the riding to help their candidate, local business leader Tony Genco. And star MPs -- Justin Trudeau and Dryden -- have been drafted to lend a hand too.

They've run a spirited campaign that's managed to take some of the shine off Fantino, zeroing in on his failure to take part in an all-candidates' debate, his controversial record as a top cop and his assertion, in his memoirs, that the Charter of Rights has most benefited criminals and members of the Hell's Angels.

Should Fantino prove impervious, the Liberals are at least likely to improve their standing in the two Manitoba byelections, which may offset a loss in Vaughan somewhat.

In Winnipeg North, longtime, popular Liberal MLA Kevin Lamoureux is up against the NDP's Kevin Chief, director of the University of Winnipeg's innovative learning centre.

Chief is considered the front-runner in the riding, held by the NDP's Judy Wasylycia-Leis for 13 years until she quit to take an unsuccessful run at the Winnipeg mayoralty. In the last election, Wasylycia-Leis carried the riding with a whopping 62 per cent of the vote.

Liberals privately gripe that the Tories are trying to ensure an NDP win by running a Filipino candidate, Julie Javier, to blunt Lamoureux's popularity in the riding's sizable Filipino community. But the NDP also got a lift from the city's leading Liberal, University of Winnipeg president Lloyd Axworthy, who provided an unofficial endorsement of Chief.

Even if he loses, however, Lamoureux is virtually certain to dramatically improve on the Liberals' paltry nine per cent of the vote in 2008.

Dauphin-Swan River-Marquette is a Conservative fiefdom, held for 13 years by Inky Mark who won in 2008 with 61 per cent of the vote. Tory candidate Robert Sopuck is considered a shoo-in this time. However, Liberals hope their contender, Christopher Scott Sarna, will improve on the meagre 14 per cent garnered by the party last time out.

Still, there's little doubt three losses Monday night would put an abrupt halt to whatever momentum Liberals still have left after Ignatieff's successful, summer-long, cross-country bus tour.

Smelling a shutout for Ignatieff, Conservative and NDP strategists are already doing their best to rub salt in the wounds.

"These byelections are a run-up to the next (national) campaign," says NDP national director Brad Lavigne.

"If a leader loses momentum here, they'll have a hard time gaining it back before the budget gets tabled in February."