There are a ton of factors that go into deciding the winner of an election campaign. Here’s one that may not be high on your list but should be: party unity.

Once the writs are drawn up by the lieutenant governor — which is the firing of the starter’s pistol for every campaign — much of the media’s and the public’s attention focuses on the leaders and their platforms.

But a cursory look back at elections past shows that winning parties tend to be the ones whose leader and candidates all sing out of the same hymn book. When even a single candidate breaks that solidarity, the results can be fatal to a party’s chances.

That may help explain why the Progressive Conservatives suddenly find themselves losing support, while the NDP is gaining. Let’s acknowledge that the Tories’ new leader, Doug Ford, has found himself in an extremely difficult political situation. He entered his role at the 11th hour, after the party had forced out his predecessor, Patrick Brown. Ford has taken over a party many of whose candidates got into politics because of Brown — and I’m told by PC insiders that many of those candidates aren’t pleased with how Ford and his colleagues have run the show. For example, Ford treated Brown harshly when the former leader was still a prospective candidate for office. (Ford said from the outset that he’d refuse to sign Brown’s nomination papers if Brown wanted to run for re-election). It may well be that Ford’s inability to keep Brown’s supporters feeling welcomed is what’s led in part to the sniping within the party that I’ve been hearing about these days.

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There’s also a sense that Ford has turned the party into his personal political vehicle. My sources within the party tell me that it’s gotten to the point where Tories have been told to add Ford’s personal Twitter handle (@fordnation) rather than the party’s official handle (@OntarioPCParty) to their tweets.

Internal grumbling during a campaign is hardly unusual. Four years ago, after then-PC leader Tim Hudak announced his plan to eliminate 100,000 public-service positions, the behind-the-scenes whispers began. Too many Tories weren’t onside with the idea, and many PC candidates’ unwillingness to defend the policy spoke volumes. After the election was over and the Liberals had secured a fourth consecutive victory, those muted whispers of dissent turned into full-fledged howls for Hudak’s head.

Back in 2007, then-PC leader John Tory was well on his way to making the unpopular Dalton McGuinty a one-term premier. But Tory’s solution to the unhappiness many Ontarians felt about public dollars funding a Roman Catholic school system didn’t sit well with some of his own caucus members. All it took was one of them — maverick backbencher Bill Murdoch — to tell reporters that Tory’s plan to offer public funding to all faith-based schools wouldn’t fly in Grey County for the avalanche to begin. After that, others began to question the policy publicly. Tory had to tap dance quickly, first playing down Murdoch’s comments and then offering a free vote on the policy in the legislature. Nothing worked. Tory’s numbers plummeted, and McGuinty became the first Liberal premier in 70 years to win consecutive majority governments.

In 2003, a PC spin doctor thought it would be cute to call McGuinty “an evil reptilian kitten-eater from another planet.” It was meant as a joke but was clearly too mean-spirited for too many people. The Tories cringed, started playing defence, and tried to distance themselves from the remark. In politics, they say, if you’re explaining, you’re losing — and the Tories ended up having to do a lot of explaining. Polls showed that then-premier Ernie Eves was already in trouble, but the fallout from the comment made any comeback impossible. Eves went on to the lose the election to McGuinty.

In 1995, Liberal leader Lyn McLeod seemed a sure bet to succeed Bob Rae as premier. The Liberals had a 25-point lead going into the election campaign. Rae’s New Democrats had had the misfortune of governing during the worst recession since the Great Depression, and the Liberals seemed poised to return to power after one term in the wilderness. But McLeod’s uneven performance in the leaders’ debate turned the campaign on its ear. Some Liberal candidates began to openly disagree with their leader, which hurt the party’s popularity. McLeod tried to put the best face on it, even saying she was proud of the dissenting candidates’ spirit of independence. It didn’t fly. On election night, Mike Harris led the PCs from third place to government — a feat that hadn’t been seen in more than seven decades.

In this election campaign, New Democrats have stayed united, despite plenty of opportunities to turn on their leader, their strategists, and their party. Several NDP candidates have made questionable and controversial comments — one disparaged the wearing of poppies on Remembrance Day; another questioned the facts of the 9/11 terrorist attacks. But so far, the party has weathered the storm.

Furthermore, the NDP research team appears to have made a $1.4 billion mistake in its platform — not an insignificant error, even with a budget of $150 billion. And yet, heads have not rolled: leader Andrea Horwath acknowledged the error, and, for the moment, life goes on. It may be helpful to the NDP that it’s the Liberals who are trying to score the biggest points off their blunder — they’re living in a glass house on this issue. Auditor General Bonnie Lysyk has criticized the governing party for coming forward with budget numbers that she says are a complete fiction. The financial dispute in that case involves $20 billion over three years and makes the NDP seem like pikers in the gaffe department.

Conversely, my internal party sources tell me, some Tories are already grumbling behind the scenes that the party’s numbers wouldn’t be falling, and that the PCs would actually have a costed platform to campaign on, had runner-up Christine Elliott won the leadership instead of Ford. While Ford is popular in some constituencies, he is a non-starter in many urban areas. I have seen numerous voters in Toronto refuse even to accept a piece of literature from canvassing Tory candidates, so hostile are they to considering a vote for a Ford-led PC Party.

So in the final two weeks of this campaign, watch for the party that demonstrates the most genuine unity throughout the entire team. Chances are, that party’s going to win.