The race for five provincial by-election seats erupted into a brawl between the Ontario Liberal Party and Toronto Mayor Rob Ford Wednesday, less than 24 hours before voters head to the polls.

Mr. Ford has been campaigning for the Progressive Conservatives, arguing that only PC candidates will build subways in his city and comparing the Grits to armed bank robbers for their treatment of taxpayers' cash.

The Liberals hit back, saying Mr. Ford has failed to do anything to build subways, while their party has put up the money to kick-start construction.

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"How can you claim to be a subway champion when you've been Rob Ford for three years and you haven't come up with five cents for a subway investment?" Transportation and Infrastructure Minister Glen Murray said outside Queen's Park. "With the mayor, it's all talk, talk, talk about subways, no one's writing a cheque. The only government that's writing a cheque is the Liberals."

The sharp rhetoric was emblematic of the bare-knuckle nature of the by-elections and yet another sign of the high stakes involved.

The votes, all in Liberal-held ridings, are the first electoral test of rookie Premier Kathleen Wynne, as well as an opportunity for Tory Leader Tim Hudak to show his party that he can win after falling short in the 2011 provincial election. New Democrat Andrea Horwath, meanwhile, has a golden opportunity to continue the slow building up of her party's small caucus.

The Liberals and Tories put their strongest candidates in Etobicoke-Lakeshore, where Councillor Peter Milczyn is carrying the government's standard against Deputy Mayor Doug Holyday. The NDP have nominated P.C. Choo. A victory there, would end Mr. Hudak's drought in Toronto while a loss for the Liberals would signal a crack in their fortress of suburban seats.

Across town, CivicAction CEO Mitzie Hunter is trying to keep Scarborough-Guildwood in the Liberals' column, in the face of challenges from Tory real estate agent Ken Kirupa and former TTC chair Adam Giambrone of the NDP. London West is also shaping up as a three-way battle between former teachers' union leader Ken Coran of the Liberals, PC lawyer Ali Chahbar and former school-board chair Peggy Sattler for the NDP. The New Democrats are looking to Percy Hatfield, a city councillor and former broadcaster, to pick up working-class Windsor Tecumseh for them. He is facing challenges from Tory Robert de Verteuil and Liberal candidate Jeewan Gill.

In Ottawa South, former premier Dalton McGuinty's constituency assistant, John Fraser, is running for the Liberals against Tory Matt Young, a sales manager, and NDP school trustee Bronwyn Funiciello.

All three party leaders have been campaigning hard. Even Ms. Wynne, in an unusual step for a sitting premier, has gone out for unscripted main-streeting with voters.

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The Tories spent Wednesday urging people upset with the Grits' spending of nearly $600-million to cancel two gas-fired power plants to use the by-elections to send a message.

"At every opportunity, the Liberals have put their party ahead of the good people of this province," PC MPP Rob Leone said. "It's time to show Kathleen Wynne … that enough is enough."

NDP House Leader Gilles Bisson, meanwhile, sounded upbeat about his party's chances: "It doesn't matter what riding you're in, people are mad at the Liberal government for all kinds of reasons … I feel quite good being on the doors in London and Scarborough-Guildwood and other places, that our candidates are going to do well."