Other indications came in a caustic exchange between Mr. Williams and Mr. McKinney at a break in the proceedings today.

"I can only believe your defense if I check my common sense at the door, and I forget the way the world really works," he told the President's lawyer, Charles F. C. Ruff, during a caustic exchange in front of the committee on Wednesday.

But a day that the two candidates had hoped to devote to some of the first substantive proposals of their campaigns quickly devolved into the sort of caustic exchanges normally not heard until close to the September primary.

As officials decide whether criminal charges are warranted against firefighters who are accused of trying to cover up an altercation between two Staten Island firefighters that left one critically injured, a firefighter familiar with the investigation said the dispute began with a caustic exchange.

Shortly afterward, she had a caustic public exchange with Malaysia's Minister of Trade, Rafidah Aziz, about Mr. Anwar's treatment.

The performance review is completed and in the process a caustic exchange transpires in which Harris directly questions her ability.

The caustic exchanges between Washington and Moscow, which many Europeans fear will knock the lid off the ash bin of cold war history, were the latest example of how the United States and Russia say they want to work together but talk past each other.

Several customers sitting in the immediate neighborhood of the bar were listening intently to the caustic exchange.

Earl tried not to sound too eager, but the caustic exchange between the couple was not only unpleasant, it put a damper on what Samantha could say.

In the second public debate of their Senate campaign, Senator John Kerry and Governor William F. Weld engaged in some caustic exchanges here Monday night over who would better champion the interests of working-class families in Massachusetts.