Justin Trudeau emerged the big winner from Monday's four federal byelections.

At first glance, the results simply preserved the status quo: the Conservatives held on to two longtime Tory bastions in Manitoba, while the Liberals retained two traditional Grit strongholds in Toronto and Montreal.

Beneath the surface, however, the byelections have roiled Canada's political waters, suggesting the Senate expenses scandal has badly hurt the Tory government and that Trudeau's Liberals are the ones who stand to benefit.

The Liberals increased their share of the vote in all four ridings _ dramatically so in two Manitoba ridings where they were all but invisible in the 2011 election, coming within a whisker of an upset victory in Brandon-Souris.

In Toronto Centre and Montreal's Bourassa riding, the Liberals emerged victorious in a battle with the NDP over which opposition party is the real government-in-waiting. Despite an aggressive challenge by the NDP, the Liberal vote share increased slightly in both ridings.

Trudeau said the byelection results show Canadians are fed up with Prime Minister Stephen Harper's scandal-plagued Conservative government and are looking to the Liberals, not the NDP, to replace it.

"Canadians grow weary of the deceit, the mistrust and the cover-ups of the Conservatives,'' he told ecstatic Liberals at the campaign headquarters of Bourassa victor Emmanuel Dubourg.

They're also discovering that Tom Mulcair is no Jack Layton, whose sunny optimism led the NDP to a stunning electoral breakthrough in 2011, Trudeau asserted.

"Make no mistake, the NDP is no longer the hopeful, optimistic party of Jack Layton. It is the negative, divisive party of Thomas Mulcair.''

Stealing a line from the late Layton's famous death-bed letter to Canadians, Trudeau added: ``It is the Liberal party tonight that proved hope is stronger than fear.''

By contrast to the Liberals' momentum, Conservative support nosedived in all four ridings _ likely the result of the Senate scandal that has engulfed Harper's government for almost a year.

Even in Provencher, which Conservative Ted Falk won with a comfortable 58 per cent of the vote, the Tory share was down about 12 percentage points from 2011. The Liberal share, at 30 per cent, was up 23 points.

In Brandon-Souris, a riding that has voted Conservative in all but one election over the last 60 years, Tory Larry Maguire barely eked out a victory over Liberal Rolf Dinsdale. He captured about 44 per cent of the vote _ a 20-point drop from 2011.

Dinsdale, who was only two points behind Maguire to increase the Liberal vote share by a stunning 38 points, said the fact the Liberals came so close to victory was a warning to the Conservative government.

"This didn't turn out the way we wanted, but it turned out better than anyone thought it would, not least of all, Mr. Harper,'' Dinsdale told a subdued room.

"(It's) a shot across the bow, we'll get you next time.''

Maguire said the Senate scandal ``certainly played a role in this campaign.''

The Tory vote almost disappeared entirely in Bourassa, where the party captured less than five per cent of the vote, and in Toronto Centre, where it scored less than 10 per cent.

For Mulcair, the results were disappointing. Despite widespread praise for his prosecutorial grilling of Harper over the Senate scandal, his party increased its share of the vote only in Toronto Centre and not by enough to steal the riding from the Liberals.

Author and journalist Linda McQuaig took about 36 per cent of the vote for the NDP, up six points from 2011 but still 13 points behind Trudeau's hand-picked star, Chrystia Freeland.

"We always knew that this was a Liberal stronghold and that it would be an uphill battle and it was,'' said McQuaig.

Still, she argued it's significant that the NDP did better in Toronto Centre this time than it did in 2011 when Layton's so-called "orange crush'' vaulted the NDP into official Opposition status for the first time in history.

Freeland had a different take.

"My message for Stephen Harper is: watch out, we're on the rise, our party's united,'' she said. "Canadians want an alternative to the Conservatives and they have found that alternative in the Liberal party.''

The NDP share of the vote declined slightly in Bourassa, despite an aggressive campaign by a star candidate, lawyer and one-time pop singer Stephane Moraille. She wound up with about 32 per cent of the vote, compared to Dubourg's 48 per cent.

In the two Manitoba ridings, the NDP vote share plunged to less than 10 per cent. The party went from a respectable second in 2011 in both ridings to a distant third.

The byelections are the first concrete measure of the Senate expenses scandal's impact on Stephen Harper's government, the depth of Trudeau's popular appeal and the durability of the NDP's 2011 electoral breakthrough.

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  • Justin Trudeau, leader of the Liberal Party of Canada, sitting on a bench in Lafayette Square across from the White House before a television interview, Washington, D.C., Oct. 24, 2013. Trudeau was on his first trip to Washington to attend a policy conference held by The Center for American Progress where he sat on a panel titled "Global Perspectives" with former Australian prime minister Julia Gillard and former U.S. secretary of state Madeleine Albright. THE CANADIAN PRESS IMAGES/Louie Palu

  • Justin Trudeau, leader of the Liberal Party of Canada, sitting in the lobby of the St. Regis Hotel, Washington, D.C., Oct. 24, 2013. Trudeau was on his first trip to Washington to attend a policy conference held by The Center for American Progress where he sat on a panel titled "Global Perspectives" with former Australian Prime Minister Julia Gillard and former U.S. Secretary of State Madeleine Albright. THE CANADIAN PRESS IMAGES/Louie Palu

  • Justin Trudeau, leader of the Liberal Party of Canada, sitting in the lobby of the St. Regis Hotel, Washington, D.C., Oct. 24, 2013. Trudeau was on his first trip to Washington to attend a policy conference held by The Center for American Progress where he sat on a panel titled "Global Perspectives" with former Australian Prime Minister Julia Gillard and former U.S. Secretary of State Madeleine Albright. THE CANADIAN PRESS IMAGES/Louie Palu

  • Justin Trudeau, leader of the Liberal Party of Canada, sitting in the lobby of the St. Regis Hotel, Washington, D.C., Oct. 24, 2013. Trudeau was on his first trip to Washington to attend a policy conference held by The Center for American Progress where he sat on a panel titled "Global Perspectives" with former Australian Prime Minister Julia Gillard and former U.S. Secretary of State Madeleine Albright.

  • UP NEXT: Memorable Trudeau Photos

  • Come At Me, Bro

    Justin Trudeau trains at Pan Am Boxing Club in Winnipeg on Friday Feb. 1, 2013.

  • Peekaboo!

    Justin Trudeau & co. making faces.

  • Riiiiip!

    Justin Trudeau splits his pants while pushing the "scrum machine" in support of Prostate Cancer Canada in Toronto Thursday, July 21, 2011.

  • Don't Shoot!

    Justin Trudeau gets his geek on at Montreal Comiccon in September 2012.

  • So Long 'Stache

    Justin Trudeau has his moustache shaved off to raise money for the Judy LaMarsh Fund, that supports female candidates, at the Liberal Party convention in Ottawa on Saturday, January 14, 2012.

  • Coming For MacKay

    Minister of National Defence Peter MacKay (left) is chased by Liberal MP Justin Trudeau in a motorized wheelchair during a wheelchair race relay on Parliament Hill in Ottawa on Wednesday, May 12, 2010. Twenty-five MPs and senators used a wheelchair for the day in support of the Canadian Paraplegic Association's Spinal Cord Injury and CPA awareness month.

  • All For One, One For All

    Justin Trudeau all dressed up for the Montreal Movember Gala in 2010.

  • Get Him!

    Pierre Trudeau's sons, Sacha, left, and Justin, tackle their mother's paperboy in Ottawa in this undated photo.

  • 'Family... And A Cow.'

    'Nuff said.

  • He Can Certainly Take A Punch

    Alexandre (Sacha) Trudeau delivers a right hook to his older brother Justin during a play fight in 1980 at Ottawa airport as the boys await a flight with the return of their father, then-prime minister, Pierre Trudeau.

  • Be Honest With Me, Who's Cuter?

    Justin Trudeau strikes a pose with an adorable baby.

  • A Very Furry Christmas

    Justin Trudeau poses with his family on his 2010 Christmas card.

  • Game On!

    Former Liberal MP Ken Dryden, left, and Justin Trudeau play table hockey as they visit Sun Youth, a community organization, Monday, Jan. 14, 2008 in Montreal.

  • Yanking Their Chain

    Then-prime minister Pierre Trudeau, left, watches as his 11-year-old son Justin swings on a chain during a tour of an old fort in the Omani town of Nizwa Dec. 2, 1983. Trudeau and Justin spent the day visiting the towns of Jebel and Nizwa 165 kilometres south of Muscat.

  • Rocking Out

    Justin Trudeau in Muskoka, Ont.

  • YeeHaw!

    Liberal MP Justin Trudeau, centre, has his cowbay taken by his son Xavier, 4 years-old, while his wife Sophie Gregoire, second from left, holds daughet Ella-Grace, 3 years-old, while they attend the party's annual Stampede breakfast in Calgary, Saturday, July 7, 2012. This is the 100th anniversary of the Stampede.

  • Like Mother, Like Son

    Eleven-month-old Justin Trudeau, urged on by his mother Margaret Trudeau, crawls up the steps of an aircraft in Ottawa on Dec. 5, 1972 to meet his father, then-prime minister, Pierre Trudeau on his return from Britain.

  • Cutting A Rug

    Justin Trudeau dances with wife Sophie Grégoire before his speech at the Liberal showcase on April 6, 2013.

  • Next: What Is Pierre Trudeau Doing?

  • Magician?

    Prime Minister Pierre Trudeau, wearing what someone called his "Mandrake the Magician outfit," walks down the grandstand steps to present the Grey Cup trophy to the victorious Montreal Alouettes in this Nov. 28, 1970 photo.

  • Hey, It Was The '70s

    Pierre Trudeau leans over to kiss an unidentified young lady to the seeming surprise of his recent bride Margaret. Trudeau and Margaret spent Saturday March 27, 1971 at maple tree farm here near Montreal at a sugaring out party.

  • Fur Wasn't Always Controversial

    Pierre Trudeau accompanies Margaret Sinclair, at the annual Governor General's skating party for members of Parliament in Ottawa Jan. 14, 1970.

  • Ditto For Seal Hunting

    Pierre Trudeau looks through the scope of his rifle while on a seal hunting trip in Baffin Island's Clear Water Fjord, July 29, 1968.

  • A Leg Up

    Pierre Trudeau shoes off his frisbee catching style while waiting to board his plane in Vancouver May 16, 1979.

  • Calisthenics Were Still Cool

    Pierre Trudeau had no trouble keeping himself occupied during a break from a boat trip down the Northwest Territories, Nahanni River, Monday Aug. 4, 1970.

  • The Outfit...

    Pierre Trudeau takes a wary look at an ice crevice, decides to chance it and makes the leap successfully during a midnight seal- hunting expedition at Clearwater Fjord in Canada's Arctic, July 29, 1968.

  • When in France...

    Pierre Trudeau receives a kiss from his wife Margaret during a tour of St. Pierre, France, Aug. 1971.

  • Running Man

    Pierre Trudeau in Guayana 1974.