10/04/2011 03:59 EDT | Updated 12/03/2011 05:12 EST

McGuinty and Hudak campaign in the south, while Horwath tours the north on Day 28

TORONTO - As the campaign for Thursday's election winds down, the three major party leaders are making their final appeals for votes.

Premier Dalton McGuinty and Progressive Conservative Leader Tim Hudak campaign in southern Ontario on Tuesday, while NDP Leader Andrea Horwath will be in northern Ontario.

McGuinty has campaign events planned for Cambridge, Bolton and Pickering.

Hudak's day has six stops — Ottawa, Madoc, Peterborough, Pickering and a pair of events in Vaughan.

Horwath starts her day at Queen's Park and heads to Sudbury in the morning and Thunder Bay in the afternoon.

Elections Ontario says nearly 625,000 people have already cast their ballot in advance polls for Thursday's election.

Preliminary figures indicate 624,958 electors voted over the 10 days of advance polling.

That is an increase from the 451,949 electors who voted at an advance poll for the 39th general election in 2007.

Advance voting opportunities included special ballot by mail, in person at the local returning office or by home visit.

Eligible voters can still vote in advance of election day at their local returning office and satellite office.

An Ottawa New Democrat has received a high profile endorsement.

Nobel Peace Prize Laureate Desmond Tutu is encouraging voters in Ottawa Centre to support NDP candidate Anil Naidoo.

"Naidoo has been an advocate for the human right to water, the rights of nature and progressive environmental causes," Tutu wrote in his endorsement.

"It's an immense personal honour to receive this endorsement," Naidoo said Monday.

Horwath slammed her two main rivals, saying they are putting their own desire for power over the needs of voters.

"To simply say: 'I want all the power for myself and if I don't get that I'm not prepared to work with anybody else' — it's kind of disrespectful to the people of the province," Horwath said after a campaign event in Brampton.

The New Democrats are going into Thursday's vote third in the public opinion polls, behind what appears to be a virtual dead heat between the Tories and Liberals.

If those trends continue, the province could be headed for the first minority government in 26 years, with the NDP holding the balance of power.

Her comments came after McGuinty ruled out a coalition or agreement with any other party, saying he was running to win a majority.

Hudak, meanwhile, has been warning that a Liberal-NDP coalition would mean higher taxes, and has said he was "fighting to win."

Hudak, meanwhile, was unrepentant about his party's decision to distribute a piece of campaign literature on sex education that the rival Liberals have branded as homophobic.

"I think they reflect (Premier) Dalton McGuinty's out-of-the-mainstream policy ideas to have a sex-ed curriculum that would begin with Grade ones," Hudak said.

Hudak, who is the father of a four-year-old daughter who started junior kindergarten this fall, said kids in Grade 1 should be learning the alphabet or math instead.

The Tory flyer urges parents to vote against the Liberals for "keeping parents in the dark" about what's being taught in schools.

Ontario's sex-ed curriculum teaches "cross-dressing for six-year-olds" and urges that teachers allow students to hold their own gay pride parade in their school, the flyer claims.

McGuinty accused the Progressive Conservatives of trying to divide voters in the dying days of the campaign.

McGuinty attacked Hudak on Monday for starting the campaign by claiming a Liberal tax credit for new Canadians amounted to affirmative action for foreign workers, and for digging up another wedge issue in the final week.

"It's rather disappointing that Mr. Hudak started off his campaign on a divisive note, now he's winding up his campaign yet again on another divisive note," McGuinty said of the Tory pamphlet.

The Tory leader is grasping at straws because he doesn't have a real plan to create jobs should the Progressive Conservatives win the election, said McGuinty.

McGuinty started the final week of the election campaign by once again visiting factories that produce components for electric cars, which he sees as a key starting point to build a green energy economy in Ontario and create tens of thousands of new jobs.