TORONTO -- Voters in the critical Greater Toronto Area dissolved their four-year-long contract with Stephen Harper's Conservatives on Monday night, returning the Liberals to the region in a near clean sweep and propelling the party to power.

Meanwhile, in the downtown core, a complete collapse of NDP support also helped to push the Liberals over the top. Liberal incumbent Adam Vaughan beat the NDP's Olivia Chow in Spadina-Fort York in one of the most hotly contested fights in the province.

"There was a red wave that went from Atlantic Canada to Ontario and I got caught up with it, on it, by it," Chow told reporters. Chow held the riding before she left in 2014 in an unsuccessful bid for the mayoralty.

"They liked me personally as a public servant...but their desire to defeat Stephen Harper was so overwhelming that they said OK, we'll go with the Liberals."

The Liberal victory in the region was decisive, encompassing Toronto proper and the suburbs. Even late NDP Leader Jack Layton's former riding of Toronto-Danforth went red.

Former Conservative cabinet ministers, Joe Oliver, Roxanne James, Chris Alexander and Julian Fantino lost their seats.

Oliver, the former finance minister, said he'd reserve his analysis of the party's national campaign. He said his team worked as hard as they could have to win the riding, but the circumstances worked against them.

"We felt quite confident until a few weeks ago that we had enough support. I had internal polls that showed us ahead, but clearly they were showing a decline in support, so the wave just swept over us," said Oliver.

"It was a continued increase in the Liberal support, and the precipitous collapse in the NDP support."

Despite having campaigned with native sons Doug and Rob Ford in the west-end Toronto area of Etobicoke twice in the past week, the Conservatives lost Etobicoke-Lakeshore and Etobicoke Centre.

Incumbent Conservatives Lisa Raitt in Milton and Erin O'Toole in Durham, two former ministers, were among the handful that held on to their seats. A close race was still unfolding early Tuesday morning in York Centre, where Conservative Mark Adler is the incumbent.

The Conservatives also faced a number of controversies around GTA candidates, including one who was caught on camera peeing in a coffee cup, and another who supported the concept of conversion treatment for homosexuals.

To understand what happened in the GTA, it's helpful to look back at the dynamics of the 2011 election, when the Conservatives swept the region in spectacular fashion.

In Mississauga and Brampton, for example, the party took every seat, whereas in 2008 they only had one. The party also pierced several elusive outer Toronto ridings, such as Eglinton-Lawrence, where Joe Oliver was elected.

Conservative party insiders point out that winning many of those ridings was because of the unique circumstances of the time -- the NDP was much stronger then under the late Layton, creating vote splits.

At the same time, then-Liberal leader Michael Ignatieff failed to capture the support of traditional party supporters -- some of them voted Conservative to prevent NDP wins in Ontario. Ignatieff lost his own riding of Etobicoke-Lakeshore -- Conservative Bernard Trottier wound up holding it for only four years.

Still, Monday's result was one of the most successful for the Liberals in history.

"This is a very, very extraordinary night," said new Liberal MP Bill Blair, a former Toronto police chief who won in Scarborough Southwest.

"I think it has exceeded anything any of us could have hoped for."