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

All three parties have been previewing their ads on the Internet -- using social media and YouTube -- which is exempt from the blackout rules.

Online ads are relatively cheaper than radio, television or print ads, so parties get the biggest bang for their buck.

Political studies professor Jonathan Rose says the parties use ads to prime the ballot box question by highlighting issues they think are relevant.

He says parties don't run ads to change opinion, but to get media coverage about their ads, which is more valuable than the cost of the ads themselves.

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.