The 2015 federal election may kick off this weekend, but an unofficial campaign has been mounting for months.

Party leaders are glad-handing and posing for folksy photo ops. Partisan ads are bragging and attacking all over the airwaves and screens of the nation. Each party's new platform policies have been previewed, debated and fact-checked in turn.

Why wait for writ drop? The game's well afoot.

Still, important things change when Prime Minister Stephen Harper makes it official.

Here's what to expect after this weekend:

Caretaker government

The Harper government has been accused of using departmental ad budgets and civil service resources to deliver partisan messages. Some of what departments have rolled out lately — child care benefits anyone? — have featured partisan branding few could miss.

But once an election is called government announcements and departmental advertising should stop.

For example, sources told CBC News that a significant federal-provincial funding announcement planned for Toyota's Cambridge, Ont. plant on Aug.7 was moved up to today.

The federal civil service continues to function, but in a caretaker role: no key decisions are made, no significant new spending is approved and no new initiatives are launched. It's status quo administration only until voters decide who's in charge.

That's why you may have noticed a flurry of ministers and MPs out this week making funding and policy announcements in photo ops across Canada: their window closes when Stephen Harper heads for Rideau Hall to request an election.

Anne McGrath, the NDP's national director, told CBC News Network's Power & Politics Thursday that cabinet ministers and MPs were out promoting over $1 billion in spending announcements on July 31 alone.

Party representatives Kory Teneycke, Anne McGrath and Jeremy Broadhurst discuss their strategies for a long election campaign 14:25

Some ads stop, new rules apply

In addition to an end for departmental advertising, different rules for third-party advertising kick in when an election is called.

Before an election, there are no rules or spending limits governing advertising by unions, issue-specific lobby groups or the much-discussed campaigns of Engage Canada and other recently-formed Canadian political action committees (PACs). They don't have to disclose their donors or how much they raise.

Engage Canada, for example, told CBC News Thursday that it continues to raise money through its website and plans to use it for more advertising before the writ period. But its spokeswoman wouldn't say how much it was making or would spend.

Political leaders like the NDP's Tom Mulcair won't have to hold their horses for an election call much longer. New Democrats have appeared hot to trot out their candidates and platform for weeks, even putting their leader on a campaign-like tour in the days leading up to the expected official launch. (Paul Chiasson/Canadian Press)

After the campaign begins, third-party groups who campaign must register with Elections Canada to disclose their activities. Spending limits apply: $150,000 maximum for a general election, although this increases if the campaign exceeds 37 days (and may be over $400,000 for an 11-week campaign).

Ad campaigns by political parties also will fall under spending limits and other rules that do not apply before the launch.

Spending limits

The Canada Elections Act limits not only advertising but all spending by registered political parties during a general election campaign.

Liberal MP Marc Garneau says calling the election early benefits the Conservatives and Canadians pay the price. 1:53

The spending limit — $25 million per party — adjusts upward for each day that a campaign is longer than the minimum 37 days, meaning it could roughly double for this fall's lengthy outing toward an Oct.19 vote.

Spending limits only kick in when the prime minister pulls the plug — before that, parties have more flexibility in where their dollars go and in what quantity.

Campaign signs

One of the most visible parts of an election landscape, the candidate lawn sign, is verboten outside of the campaign period.

But those who want to put one up don't have long to wait before it's legit to stake a preference. Choose locations carefully — depending on where you live, they might be up for a very long time.

Or not — check with your local authorities. The City of Ottawa, for example, has a municipal by-law that says election signs may not be posted on public property until 30 days prior to an election, or on private property until 60 days before.

Bills die, Senate pauses

When Parliament dissolves, the House of Commons stops. Speaker Andrew Scheer becomes a Conservative candidate for re-election in Saskatchewan.

Liberal Leader Justin Trudeau has been using his personal appeal to draw attention (and funds) back to his third-place party. But in the context of a long campaign, will money for attack ads speak louder than photo ops? (Darryl Dyck/Canadian Press)

All bills left unpassed on the order paper die. Commons committees cease to function.

The Senate, however, does not run for re-election. Its administration continues, even as its legislative function is on hold.

Senate Speaker Leo Housakos suggested last month that it may continue to consider some matters, like the ethics investigation into former Conservative Don Meredith.

Some Senate actions only apply to the current Parliament — such as the decision to suspend three senators caught up in the ongoing expenses scandal. As Mike Duffy's fraud and breach of trust trial resumes Aug. 12, he will be back on the payroll.