TORONTO -- A bombardment of partisan advertising will rain down on an unsuspecting Ontario public starting Wednesday as the ban on election ads is lifted.

Voters already have a taste of what to expect, with all three parties previewing many of their ads on the Internet and through the news media, both of which are exempt from the blackout rules. But now they'll have the keys to the traditional media kingdom, including television and radio.

The parties aren't running the ads to change opinion, but to get media coverage about their ads, which is more valuable than the cost of the ads themselves, said Jonathan Rose, a political studies professor at Queen's University in Kingston, Ont.

They also use the ads to prime the ballot box question by highlighting issues they think are relevant, he said.

"I think we can expect to see broad general feel-good ads at the beginning and then particular pointed ads towards the end of the campaign, depending on post-debate what's happening and where the poll numbers are and what the hot-button issue is," he said.

The Liberals, who are promising to run a positive campaign, gave a sneak preview Tuesday of their first TV ad on YouTube, which they say will run during commercial breaks on breakfast chat, news and prime-time shows.

It shows Premier Kathleen Wynne slamming Progressive Conservative Tim Hudak's promise to cut 100,000 jobs in the public sector to help create half a million more in the private sector, saying he would cut teachers and health care.

Wynne said she wants to "build Ontario up, not tear it down" by investing in infrastructure, provide fair pensions and create jobs.

The Liberals say they're not going negative, just trying to show the contrast between the two parties.

"That's not a negative ad," said campaign co-chair Tim Murphy. "That's a positive ad speaking to the choice that this election presents the voter."

But there are positive ads that are negative, said Rose.

Jimmy Carter ran an ad talking about family values, which was a huge slight against Ted Kennedy -- who was seeking the Democratic nomination against Carter -- in the lead up to the 1976 U.S. presidential election.

The Progressive Conservatives have also vowed to run a positive air war, starting with an ad that highlights their plan to create jobs.

It depicts three people of different professions -- a tool-and-die maker, a chemical engineer and a welding inspector -- who want to work, as Hudak speaks in the legislature about Ontario's "jobs crisis" and how the province needs to try a new approach to create jobs.

Soon after the ad debuted on YouTube on Monday, the Liberals posted their own re-mix, with all three people saying their jobs were cut by Hudak. It was later removed "due to a copyright claim by Ontario PC Party."

Rose says the leaders' tour is supposed to be positive and upbeat, while the campaign dynamics behind the scenes in the party war rooms are often "unsavoury."

Negative ads are character assassinations, unfounded allegations or claims made without any data, he said. Businesses don't run them because they can affect people's disposition towards the entire brand.

If one airline ran ads saying another airline's planes are unsafe and the second airline said the other's jets were cramped, then it makes all airline passengers feel like they don't want to fly, Rose said. Similarly, running a negative political ad can affect voters' confidence in democratic institutions and politics, so they don't want to vote.

"Negative ads really poison the well," he said.

The Tories have bragged about making the largest online ad buy in Ontario political history. Online ads are not only exempt from the blackout rules, allowing the party to advertise earlier, but are also relatively cheaper than radio, television or print ads, so parties get the biggest bang for their buck.

The Conservatives say they're also buying television, radio and print ads, but the way in which voters consume information is vastly different in the digital age, said Tory spokesman Will Stewart.

"We just think it's not the 1980s anymore and there's no sense in advertising like it's the 1980s," he said.

Party strategists also say they're looking at targeting certain voters. Wynne has voiced 35 different radio ads for different markets.

Others say geography, language and timing are all part of the calculation of where and when the ads air and how they're tailored. Some ads may run in certain ethnic and culture newspapers, radio and TV shows, for example.

An NDP strategist says they're targeting undecided voters, who they believe will decide the outcome of the election. They have their eye on those who may have voted Conservative in the past but don't like Hudak, who helped turn one Conservative riding orange in a London byelection.

The party has bought a "wrap" -- a cover page -- of one the large daily newspapers whose readership isn't typically associated with NDP voters, but "shaded more blue."

A blackout at the beginning of a campaign is only imposed if there's a snap election call and is aimed at preventing the governing party from gaining an edge by having political advertising ready to go as soon as the vote is announced.

A second blackout period begins at midnight on Tuesday, June 10 and ends at 11:59 p.m. on election day.