OTTAWA – What voters will decide on Oct. 19 is beyond the Conservatives’ control. But one thing is firmly in their grasp: when to drop the writs that will take them to the polls.

Exactly what day Prime Minister Stephen Harper will visit the Governor General to make the formal request to dissolve Parliament and call the election has been the source of weeks of political speculation. And with good reason – it’s ultimately a political calculus of the Conservatives’ own devising.

READ MORE: Fact file – Federal campaign periods and spending limits

Although a law passed in 2007 set a fixed election date for Parliament, it didn’t set a fixed length on how long the election campaign could be, only how short – no less than 37 days including the day it begins.

Fast forward to 2014 and the introduction and subsequent passage of the contentious Fair Elections Act, which among other things changed the rules around campaign finance.

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In short – the longer the campaign, the more everyone can spend.

READ MORE: Fixed-date election comes with concerns, observers say

As the party sitting on the biggest war chest, there’s no question the Conservatives would want to start the election sooner rather than later, the New Democrats suggested.

“Word is Stephen Harper could call the election early, in as little as 25 days,” reads a fundraising pitch sent by the party last week.

“It’s not hard to see why – the longer the election, the more money the Conservatives can spend attacking us.”

The sooner the writs are dropped, the sooner the Conservatives could also potentially curb third-party groups like Engage Canada, a union-backed organization currently running ads against them, much to their frustration.

Right now, groups like that also have no limits on spending, but if they spend $500 on ads after an election call, they must register as a third party. Then, limits come into effect, though they are also increased according to the length of the election.

Then there’s the other side of the political coin.

Once the election has begun, government institutions can no longer advertise unless they have a legal obligation to do so or it’s a public safety matter.

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At the same time, limits are imposed on what political parties can spend.

So, among the calculations being made in the Conservative war room is what’s worth more – attack ads on their opponents, funded by party dollars that are limited by law; or limitless taxpayer-funded ads they could be running promoting their policies.

For a while, they were doing both in tandem. Health Canada at one point had an ad campaign against drug abuse which was running at the same time as a radio ad from the Conservative Party attacking Liberal Leader Justin Trudeau for his stance on the legalization of marijuana.

Just last week, the department announced it was putting its drug-abuse campaign back on the air until Aug. 8.

That’s around when most Conservative insiders think Harper will go to Rideau Hall.

Government spending announcements are on the calendars for some departments right up until the end of July, though this week’s roll out of the universal child care benefit cheques is considered among the final major things on the government’s to-do list before formally going to the polls.

Then, there is the first leaders’ debate, set for Aug. 6, which will allow Harper the opportunity to set a political tone and potentially gather footage that can be turned around immediately into advertising.

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Meanwhile, some staffers have been told to make sure their bank accounts are flush enough by mid-August to cover off their rent for a few months, as many will be taking unpaid leaves of absence to work on the campaigns.

That’s not to say campaign planes will take flight right away. Harper told MPs in June he had no intention of spending all of August traipsing across the country. It’s more likely that the official machine won’t rev up fully until Labour Day.

He has, however, cancelled his usual August trip – the annual tour to the Arctic.

There’s no word on whether the Governor General has also been told to clear his calendar in early August to formally kick start the vote. Rideau Hall never discusses anything related to politics.

And from the prime minister’s office itself, only two words:

“Stay tuned.”