The ad Rendell referred to - the only one Casey had on the air in Philadelphia for a time - depicts an image of Smith on a tea cup and suggests the GOP nominee is too far right politically for Pennsylvania.
Shorr, speaking to The Inquirer, said Rendell appeared unaware that Casey has two ads on the air in Philadelphia (and will start a third Saturday). He said Casey has run seven commercials statewide.
"His quote was all he's seen is one ad; 'He is not running a real campaign,'" Shorr said of Rendell's remarks. "Well, we've been on the air in Pittsburgh and Johnstown since Aug. 1 with seven different ads.
"I guess it's obvious that [Rendell] didn't know that," Shorr said. "But I guess that's why the people who live out there thought when he left office that he was governor of Philadelphia."
Casey, a first-term senator, and Rendell, a two-term former governor and one-time Philadelphia mayor, are Pennsylvania biggest-name Democrats.
This war of words comes 2 1/2 weeks before the Nov. 6 election, with polls showing that Smith has narrowed Casey's lead.
Larry Smar, Casey's campaign manager, said Smith, a coal-mining millionaire, has donated $17 million of his own money to his campaign and has spent $7 million on TV. Casey, he said, has spent $5 million on TV.
In Philadelphia, Casey didn't start running commercials until about Oct. 1.
"We let [Smith] spend $2 million to our zero," Shorr said. "But we saved our money to be able to match him in the end in southeastern Pennsylvania. And from every indication we have from out polling, that strategy is working."
Some recent public polling has suggested that Casey leads by only a few percentage points. Shorr said the Casey camp has its own new poll showing the Democrat up by 13 points, 52-39.
Rendell, in his comments to the Scranton paper, expressed confidence that new Casey ad spending would stop the damage done by Smith and that Casey would win the election.
Jim Conroy, Smith's campaign manager, said the Democratic spat made it clear that Casey "is on the defensive."
He said Smith's polls show a "very, very close" race.
Contact Tom Infield at 610-313-8205 or firstname.lastname@example.org, or follow on Twitter @tinfield.