TORONTO -- With just hours to go before Ontario voters head to the polls Thursday, accusations of dirty tricks are flying on the campaign trail.

The Progressive Conservatives were incensed Wednesday about a Liberal flyer substituting Tory Leader Tim Hudak as the psychopathic Joker from the Batman movie "The Dark Knight."

The flyer, which was distributed in a Liberal riding north of Toronto, depicts Hudak laughing as he walks away from an exploding hospital.

The question beneath the picture asks voters if they trust Hudak and the Ontario PCs with their future.

"I haven't seen the piece of literature, but this kind of campaigning is not acceptable," Premier Kathleen Wynne said during a stop at a Toronto elementary school.

"It's not consistent with what we have been doing throughout this campaign."

Steven Del Duca, who holds the riding of Vaughan, apologized to Hudak over Twitter, saying it "was a mistake for which I am sorry."

Tensions are high as public opinion polls have suggested the Liberals and Tories are in a virtual tie, with just a few hours left before voters start casting their ballots.

The Tories called the flyers "terrorist literature," saying it's fear-mongering at its worst to scare voters into voting Liberal.

Wynne is running a "campaign of fear," Hudak said during a campaign stop in Mississauga, west of Toronto.

"I know that Kathleen Wynne began her day yesterday in a school, saying that our plan is going to hurt children, and she finished the day yesterday with an over-the-top flyer with me laughing in front of a hospital blowing up," he said.

"That's way across the line, and the Kathleen Wynne that I used to know would never have stooped to that kind of tactic to cling to power. When you go that far, when you go over the top that much just to hang on to your job, it's time to pack it in -- you're no longer there for the public interest, you are there for yourself."

But the finger-pointing didn't end there. Allegations of Liberals illegally taking down a Tory campaign sign were countered with recriminations that the Tories had broken the rules by putting the sign up in the first place.

Tory complaints that the Liberals were breaking the media blackout on partisan ads were met with outrage from the Liberal camp, which said it had run them by election officials in advance.

There were also accusations of deliberate voter suppression efforts on Tuesday after dozens of voters in London and some in Ottawa received letters directing them to the wrong polling station.

The Tories said it was an innocent mixup and apologized, with Hudak saying they had just made mistakes. But the Liberals have filed a complaint with Elections Ontario.

New Democrat Leader Andrea Horwath said the Liberal-Tory shootouts show "a little bit of last-ditch desperation."

"There's no doubt that there has been that tenor in the last couple of days, but I think the stakes are high," she said in Oshawa.

"Not necessarily the stakes being high for the politicians, but the stakes are high for the people of this province. They deserve much better than what they've had in the last number of years."

The rapid-fire war-room missives came as leaders of all three main parties were making a final push for votes before polls open Thursday morning.

Wynne stayed in vote-rich Toronto, visiting five NDP-held ridings that the Liberals hope will swing their way. She also planned to visit the PC riding of Etobicoke-Lakeshore -- the Tories' only Toronto seat -- which was previously held by a Liberal cabinet minister.

Horwath was also making eight stops at non-NDP ridings in Mississauga, Brampton, Toronto, Oshawa, Belleville and Kingston.

Hudak headed to Waterloo and Niagara Falls and was to end the day in Jarvis with a town hall meeting.

At dissolution, the Liberals held 48 seats in the 107-member legislature, the Conservatives 37, the NDP 21 and one vacant.