Democrats say progressive groups were flagged as well as tea party organizations. They say the investigation has turned up no evidence that any extra scrutiny was given to applications from conservative groups for tax-exempt status.
Issa told reporters Wednesday that the hearing was a continuation of an earlier meeting where lawmakers had already made opening statements.
After the hearing, Issa told Fox’s Greta van Susteren that Cummings "didn't have a question. He was endlessly slandering the efforts of the committee."
Issa has headed the House's top investigative committee since his party took control of the House after the 2010 election. He must give up the gavel at the end of this session because of GOP-imposed term limits on chairmen.
The brouhaha brought back memories of a 2003 House Ways and Means Committee hearing that exploded into a near-brawl as insults like "wimp" and "fruitcake" were exchanged and the Capitol police were summoned.
Reps. Pete Stark (D-Hayward) and Scott McInnis (R-Colo.) were said to be ready to exchange blows, but Stark, then 71, later ridiculed that a fight was about to erupt.
"I'm an elderly gentleman," he said. "I haven't been in a fight involving bodily contact for over 60 years.... Look, I fall over trying to put on my underwear in the morning."