See the list below for more on what we might expect:
There is no crystal ball
According to current polls, the NDP needs to gain support to move out of its third-place standing. The most recent by Nanos Research shows that the NDP's Andrea Horwath trails Liberal leader Kathleen Wynne in the "make the best premier" category.
But polls in advance of elections over the past few years have ended up being wrong, says Cathy Worden, vice president of public affairs at Hill & Knowlton Strategies.
"We have recent examples in Quebec and B.C. where the way things have started out have completely turned on their head in the way that they have ended with results on E-Day," she said. "Absolutely anything can happen in this Ontario election."
Personal stakes are high
The NDP has propped up the minority Liberals over the last two budgets, but this move signals a much larger gamble on the part of the party.
Horwath is gambling and the stakes are high. She stands to win more seats and an increased caucus in a re-elected minority Liberal government, but she stands to lose if Conservatives win a majority government — and the election could result in any iteration of government.
She has doubled the NDP caucus since taking control of the party in 2009 — with a strong performance in the 2011 general election and during the leaders’ debate — and decisive wins in byelections in 2011, 2012 and last year in ridings without an NDP tradition.
"Whatever direction Horwath goes, there are risks, because while her party's future is at stake — so, too, is hers as leader," said CBC.ca's provincial affairs specialist Robert Fisher.
The stakes are high for Ontario Progressive Conservative leader Tim Hudak as well, who was overshadowed Saturday by Prime Minister Stephen Harper's foray into the provincial election. Harper lashed out at Wynne's proposal for a provincial retirement plan, calling it an "unnecessary tax hike." Wynne says the prime minister appears to be "taking over the Conservative voice in the Ontario election."
"I find it hard to believe that if either of those opposition leaders are not successful on Election Day that their parties will allow them to stay as leaders," Worden said of Horwath and Hudak. "The stakes personally for those leaders are quite high."
Anything can happen
The results of the election and who actually comes out on top and wins is all going to come down to how people feel on Election Day, Worden says.
"People are going to wake up on June 12 or the day that they go to their advanced polls and they're going to feel a certain way about the parties, the leaders, what they want for the province, and they'll make a decision then. That's what it's all going to come down to."
Liberal Party scandals will take centre stage
Scandals surrounding the costly cancellation of two gas plants, the Ornge air ambulance service and potentially unsafe girders that were installed on a parkway in Windsor were reasons Horwath gave for jumping ship on supporting the Liberal budget, and they show no signs of fading as ammunition for Wynne's opponents during the campaign.
"With Wynne coming into power 15 months ago and especially with the scandals that the Liberal government has had to deal with, the public is quite aware and sensitized to the fact that the political parties have been in campaign mode for a number of months, especially with the run-up to the budget," Worden said.
The NDP X-factor
Hudak has released white paper after white paper to put forth his vision of job growth and austerity measures are the Conservatives' foundation for a campaign platform. The same goes for Wynne's election budget, which is essentially a platform for the Liberal Party .
"There's no secret there that they have been preparing for an election and have laid out exactly where they stand on the issues," Worden said.
"The X-factor is that the NDP has not yet released its plan, so how and when the NDP releases its plan is going to be quite interesting in terms of how that will affect the election.
"The trend we have seen recently is platforms are released slowly, over a number of days. That allows for a longer media cycle and more time for the public and the electorate to absorb the information in each part of the platform."
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