The ads, which were placed through Google and appeared on other, less-partisan, news sites as well - were a quick and easy way for the Allegheny County executive to raise his profile among liberals who didn't know much about him but were unhappy with Corbett's Twitter subpoena.
It also pointed to something more important: The role that not only the wider Internet but also social-networking sites that were barely known the last time Pennsylvania elected a governor in 2006 now play in gaining new supporters, and firing up the ones they already have.
Last month's U.S. Senate primary in which Democratic U.S. Rep. Joe Sestak ousted longtime Sen. Arlen Specter was hailed by many as a triumph of so-called "old media" - specifically, a TV commercial blasting Specter's party change known as "The Switch."
But campaign aides to Sestak are quick to note that "The Switch" also was viewed about 88,000 times on the candidate's channel on the video-sharing Web site YouTube.com, reaching voters in areas of the state where it wasn't as cost effective to use extensive and costly TV.
"The congressman really believes in the power of video to get his message out," said Sestak's new media director, Tom McDonald - so much so that the Delaware County congressman created two channels on YouTube, a positive one as well as an attack site called The Real Specter.
It was in 2004 that the media first marveled at the power of the Internet to boost a candidate - most notably Democrat Howard Dean, whose campaign built close relationships with progressive bloggers that put the then-obscure Vermont governor on the radar screen. Six years later, those days seem quaint.
In 2010, candidates sometimes are measured less by the dollars they've raised than by the number of their friends on Facebook. Commercials that would have cost hundreds of thousands of dollars to broadcast are downloaded onto the Internet and then promoted for free by 140-character "tweets" on Twitter.
And online display ads can pinpoint only Pennsylvanians through the technique of "geo-targeting," saving cash while assuring that locals are saturated with the intended message.
In Pennsylvania, the political wars of 2010 may be won on the playing field of Twitter.
John Brabender, a longtime Pennsylvania campaign strategist working for the Corbett campaign, said that as many as 15 to 20 percent of a candidate's ad budget now goes to new media. In part, he said, that's because viewers increasingly have tuned out the kinds of TV ads that came to dominate U.S. politics starting in the 1980s.
Now, it's a lot more valuable to spread political news through trusted friends on Facebook or Twitter. "If you get one friend to tell another friend something, that's more effective," Brabender said.
If so, that may be good news for the candidate who arguably entered the year with the biggest online following already, Republican Senate candidate Pat Toomey, a former congressman from the Allentown area who nearly ousted Specter back in 2004 when Specter was still a Republican.
ToomeyForSenate had the most followers on Twitter of any major Pennsylvania candidate as of last Friday, with 4,907, although his lead is not that large over Sestak2010, which had 3,796 followers.
The lower profile for the governor's race so far is reflected by the fact that CorbettForGov has only 806 followers, while Dan_Onorato has just 783 followers.
Campaign officials said that Twitter is increasingly seen as a tool to energize the exisiting base of supporters - by letting them know in short blasts when the candidate is coming to town or empowering them to spread word of a new ad and counter a rival's attack - rather than woo new ones.
"Mobile and Twitter don't matter as much (until Election Day) as Facebook and Google, because what people do online more than anything else occurs on those two platforms," said Michael Cornfield, an adjunct professor in political management at George Washington University whose specialty is online politics.
Facebook, which includes space for multiple pictures as well as biographical or issues information, is viewed as a place where undecided voters might get to know the candidate.
If that's true, that may be bad news for the Democrats in November. Toomey's Facebook page had, as of Friday, 10,361 friends, and his GOP ticketmate Corbett had 8,430. In contrast, Onorato had 3,618 friends and Sestak trailed with 3,146.
Tim Kelley, who deals with online media for the Toomey campaign, said that so far the advantage has been using the social networking sites to share and reinforce messages with supporters. "Without Twitter and Facebook, there's a lot of online advertising that nobody would see," Kelly said.
Sestak's deficit in social networking is somewhat surprising, since his upstart challenge seemed rooted in the active online blogging community of liberals, which clamored for a progressive challenger to Specter from the time he switched parties in May 2009.
But Sestak's aides point out his success in luring Internet users to watch campaign ads on YouTube was critical, with more than 200,000 viewers signing up for the two channels.
His ticketmate, Onorato, may be lagging a bit, but campaign spokesman Brian Herman said winning the nomination last month will bring him up to speed quickly. "We now have a statewide base of support, and Dan hasn't run statewide before," he said.
The Corbett episode that some dubbed "Twittergate" - in which Corbett issued a subpoena to Twitter in an effort to learn whether an online critic was a specific defendant awaiting sentencing in a criminal corruption case - was only natural fodder for a campaign aimed at heavy Web users.
The Corbett move already had generated outrage among many users of Twitter, a service that wasn't even invented before 2006 but now seems integral to political messaging.