Corbett's campaign spokesman Kevin Harley dismissed the ad Thursday as "the liberal mayor of New York writing a big check to a liberal organization."
Harley also called the ad "factually inaccurate." He said Ryan Hacke, the baby whose photo is in the ad, died in 1997, four years before Pennsylvania reached a gun permit "reciprocity agreement" with Florida. The boy's mother, Mary Beth Hacke, makes no direct claim in the ad that the agreement led to her son's death - merely that a loophole in the law needs closing to prevent other gun deaths.
Corbett's Democratic opponent, Dan Onorato, said that he had heard little about the spot and that neither he nor his campaign had any role in its creation.
Bloomberg made no secret of his role in the ad. The mayor donated to CeaseFire PA knowing the money would be spent in support of Onorato and other pro-gun-control candidates, Bloomberg spokesman Jason Post said Thursday.
"The donation was made to the group, but the larger point is that the mayor is supporting candidates from all parties that share his stance on this issue," Post said.
The so-called Florida loophole has reared its head in several of the state's races this campaign season.
Because Pennsylvania has agreed to honor "concealed carry" gun permits from other states, most notably Florida, gun owners here can obtain nonresident licenses through the mail, even without a Pennsylvania permit.
Critics, including some law enforcement officials, call this a loophole and point to it as a factor in several recent deaths, including the September shooting of 18-year-old Irving Santana in Philadelphia's Olney section by a convicted felon whose Pennsylvania permit had been revoked.
Last spring, CeaseFire PA sought pledges from gubernatorial candidates to revise the law. Onorato agreed; Corbett did not respond, said Joe Grace, executive director of the Philadelphia-based advocacy group.
Since then, Onorato has pounded Corbett on the issue.
"I think it's an outrage that he doesn't support" ending the practice, Onorato said Thursday as he shook hands with rush-hour rail commuters at a SEPTA station in Jenkintown. He described his own position not as an attack on gun owners' rights but rather a bid to enforce registration laws already on the books.
Corbett, for his part, disputes the notion that a loophole exists. "Florida has stricter standards than Pennsylvania," among them a fingerprint requirement and mandatory firearms training, said Harley, Corbett's spokesman.
He also noted that as attorney general, Corbett helped create a gun task force in Philadelphia that has been responsible for 400 arrests.
Corbett's campaign has enjoyed support from the National Rifle Association, which has aired ads supporting him in central and western Pennsylvania.
The CeaseFire PA ad is not the first time Bloomberg, a Democrat-turned-Republican-turned-independent, has involved himself in Pennsylvania politics or in the gun-law debate nationally. In the past he has joined Gov. Rendell in calling for tougher gun restrictions. In August, he chowed down on cheesesteaks during an endorsement visit for Joe Sestak, the Democrat running against Republican Pat Toomey for Pennsylvania's open U.S. Senate seat.
And Americans United For Safe Streets, a Bloomberg-backed group, launched a mail campaign on Tuesday criticizing GOP congressional candidate Patrick Meehan's stance on the Florida permit issue. Meehan's opponent in the suburban Seventh District, Bryan Lentz, has advocated changing the law.
CeaseFire PA spent $300,000 of Bloomberg's donation to fund the anti-Corbett ad buy - enough to ensure that typical TV viewers will see the spot six to eight times before Election Day, Grace said. He said the group planned to use the rest of the money in support of other candidates.
"The old saw has always been that you can't talk about this issue in a Pennsylvania election," Grace said. "That's changing, and we are proud to have the support from someone we view as a national leader in the fight against illegal guns."
Contact staff writer Jeremy Roebuck at 610-313-8212 or email@example.com.
Inquirer staff writers Amy Worden and John P. Martin contributed to this article.