OTTAWA -- The longest election campaign in modern Canadian history hits the midway point this week and political parties are ramping up their advertising wars.

Under new changes brought in last year by the Conservative government, campaign spending limits increase with the length of the writ period, meaning a party with a full slate of 338 candidates this year can spend almost $54.5 million.

According to Elections Canada returns, the big three national parties spent between 39 and 50 per cent of their 2011 election campaign budgets on TV and radio advertising -- a combined total of $28 million, not including "local" ads by individual candidates, who have their own spending limits. If the same proportions hold true this year, the Conservative, New Democrat and Liberal national parties could pour an unprecedented $20 to $30 million each into their respective air wars, plus millions more in regional ads by local candidates.

All that ad spending is not evenly spread over the length of a campaign. Parties tend to go heavy in the first week as each tries to establish the ballot question, ramp up again around the major televised leaders' debates and then go all out over the final 10 days, when voters are firming up their choices.

This year's 11-week campaign -- from Aug. 2, when Prime Minister Stephen Harper asked that Parliament be dissolved, to election day Oct. 19 -- has introduced a new advertising dynamic. So has the unusual three-way race that has the NDP, Liberals and Conservatives all within hailing distance of one another.

Political parties don't divulge their media buy strategies, and many advertisements that are floated in party announcements never actually air on TV. However, given the increasing importance of web viewership, the once-clear distinction between ads that merit a TV buy and those that only run online is blurring.

"Advertising is a window to the campaign," Jason Lietaer, the president of Enterprise Canada who ran the Conservative campaign "war room" in the 2011 election, wrote in a blog post this week.

"There's lots of ways to figure out where the parties think they stand, but they pay a lot of attention to advertising. It's where the real money is spent and it has the potential to move a larger number of votes more quickly than any other medium."

Suffice it to say, you ain't seen nothing yet.

Here's a look at the state of play in the ad wars through the first five weeks of the 78-day campaign:

Conservatives:

The deep-pocketed governing party has been blanketing the airwaves with ads attacking Justin Trudeau since last May, long before the official campaign began. "The Interview" series, in which actors pretend to examine Trudeau's resume before declaring him "just not ready," was a fixture throughout August on everything from news channels and sports networks to specialty channels such as Discovery and the Space Channel, according to sightings posted on social media.

The Conservative party has aired at least five different versions of "The Interview," focusing on different issues and claims about Trudeau's platform. NDP Leader Tom Mulcair gets the treatment in one version.

Harper, with a nine-year record to run on, has been largely absent from the Conservative ad campaign so far. A new English-language Conservative ad features actors talking about the leadership options and ends with a white-haired woman earnestly stating: "Stephen Harper isn't perfect, but when it comes to the economy we can depend on him." A new French-language ad being shopped by the party this week paints Tom Mulcair's NDP as "too risky."

Here's a peek:

New Democratic Party:

The NDP has been leading in national public opinion polls since the official campaign began and have coasted on that front-runner status with an almost non-existent media buy until this week, presumably mustering their resources for a big push later in the campaign when they hope to seal the deal.

A new, soft-focus NDP ad narrated by Mulcair is going into paid circulation this week, while a hard-hitting attack ad targeting a list of Harper appointees in legal difficulties generated plenty of online buzz and earned media but did not appear to be the subject of a significant media buy.

Here's a peek:

Liberals:

The Liberals under Trudeau have faced paid Conservative attack ads literally since the day Trudeau was chosen party leader in April 2013. The barrage only intensified with the start of the election campaign last month and the Liberals responded with a paid election ad that appeared to break one of the cardinal rules of politics: it repeated the language of an opponent's criticisms. Nonetheless, the ad with Trudeau declaring himself "ready" to govern appears to have received a significant financial push, appearing everywhere from NASCAR, baseball, soccer, Canadian Football League and NFL preseason telecasts to the Food Network and at least one episode of Citytv's "Bachelor in Paradise."

A more recent ad featuring Trudeau talking about the economy while on an escalator is also getting paid air time, according to social media sightings.

Here's a peek:

Green party:

There's no evidence that Elizabeth May's Green party is running any paid national advertising yet but the party did get a minor earned media coup with the release of an online campaign ad featuring Green candidate and former TV meteorologist Claire Martin reprising her on-air persona with a "political" forecast.

Here's a peek: