To put it plainly, winning an election means winning more ridings than any of the other parties. Ideally, you have so many more that your party forms a majority government.

The CBC Decision Desk will be looking at the early results from a handful of key Ontario ridings on election night to see where things are headed and for an early idea of which party will end the night with the most seats.

Here are 12 ridings to watch to gauge the parties' fortunes.

Can the PCs defeat the Liberals?

The Progressive Conservatives need to win all the ridings they won in the last vote and pick up wins in 17 more in order to win a majority government. That’s a tall order.

To win a minority government, the PCs need to make some solid gains. Here are five "must" wins for the PCs. If they are not picking up these, then it could be a bad night for PC Leader Tim Hudak:

Ajax Pickering – PC candidate Todd McCarthy tried and failed to win this riding in the 2011 election. The riding has a political history that favours Conservatives, having in the past elected the late Jim Flaherty and Janet Ecker, a senior cabinet minister in the Mike Harris government. This is one of the ridings in the 905 belt around Toronto that Hudak needs to win.

Brant – The PCs lost here in the last election by just 1,106 votes. This time, they are running Phil Gillies and hoping for a political comeback. Gillies held this riding for the PCs for nearly a decade in the 1980s.

Glengarry-Prescott-Russell – This is a mostly rural riding in eastern Ontario, a region where the PCs have been polling well throughout the campaign. The PCs lost to the Liberals here in 2011 by 1,372 votes. If the PCs are winning here, it’s a good sign that they could end up with the most seats at the end of the night.

Kitchener Centre – The PCs very nearly defeated former Liberal cabinet minister John Milloy in 2011, losing by just 323 votes. Milloy is not running again. PC candidate Wayne Wettlaufeur, who won in Kitchener for the PCs in 1995, is going for a political comeback. (Read more about Kitchener Centre)

Peterborough – This is the classic Ontario bellwether riding. Voters here have picked the candidate from the winning party in every election since 1977. A PC lead in the early going here on election night would be a good sign for Hudak.

How do the Liberals win?

Just as Liberal Leader Kathleen Wynne found herself attacked from both sides at the debate, so too is the Liberal campaign across the province. In some ridings, the fight is against the NDP. In others, it’s against the PCs. There are few real three-way races anywhere in the province. The key to a Liberal win is to offset losses in some ridings with gains in other ridings, all the while holding as many of the seats that they can from the last vote.

At the end of the night, if the Liberals are just plus-five on that calculation, they will be back at Queen's Park with a majority government.

Here are three ridings that the Liberals almost certainly need to get on the plus side of the ledger to get to that number:

Davenport – The Liberals lost this riding to the NDP in 2011 in a close race when the longtime Liberal incumbent did not run again. This time around, with polls showing the Liberals with considerable support in the Toronto area, they need to take it back.

Etobicoke Lakeshore – The Liberals lost this riding in a byelection to former Toronto deputy mayor Doug Holyday, who got an assist from Toronto Mayor Rob Ford and Ford Nation. Holyday is not getting any help like that this time. A strong Liberal lead here would be an early sign of a good night for Wynne. (Read more about Etobicoke Lakeshore here.)

Bramalea-Gore-Malton – The NDP won this riding in 2011 with a comfortable 2,277-vote margin over the Liberal incumbent Kuldip Kular. This is a rematch between the two. NDP Leader Andrea Horwath has been campaigning hard in this riding to keep it New Democrat. If it is falling back into Liberal hands, it's a signal the Liberals could be on their way to a majority win.

How does the NDP fit in?

As much as it was the New Democrats whose decision to reject the Liberal budget triggered the election, how well the NDP does on election night will decide if the Liberals win or lose. While anything is possible (as we saw in the Bob Rae NDP win in 1990), it appears unlikely that the NDP will win more seats than either of the other two parties. However, the NDP can claim a victory if it comes out of this election with more seats than where it started.

Here are two ridings to watch that will offer an early signal about how the NDP will fare:

Sudbury – The popular and longtime Liberal incumbent Rick Bartolucci barely managed to hang on against the NDP in 2011, pulling off a win by a mere 531 votes. He is not running this time. If the NDP is going to gain seats, this needs to be one of them.

Windsor West – This would be a big win for the NDP on election night. If local school board trustee Lisa Gretzky can defeat Liberal cabinet minister Teresa Piruzza, it could be a sign that the NDP might end the night with more seats than it started with.

On the other hand, if the NDP are losing these two seats, then it’s a sign of a long and potentially bad night for Horwath:

Trinity-Spadina – This longtime NDP riding held by Rosario Marchese is a must win for New Democrats. But, it's a riding that is changing demographically and where there is a concurrent federal byelection taking place. Reports are that Liberal candidate Han Dong has run a strong campaign.  

Kitchener Waterloo – NDP candidate Catherine Fife won this riding by a comfortable 3,748-vote margin in a byelection in 2012. This riding had been won by the PCs since it was created in redistribution in 1999.