Such exchanges underscore the peculiarity of Mr. Johnson's relationship with his boss.

Hezbollah was established by Iran to help counter that Israeli invasion, and today's exchange underscored both the duration and the fury of the conflict that has followed.

The exchange between Mr. de Blasio and Ms. Eggleston underscored confusion over the waiver, which is available to regions with insufficient jobs.

One e-mail exchange, from the company's chief ethics officer to a lead investigator, also underscored that those overseeing the operation were worried that their efforts could invite legal scrutiny.

The exchange underscored just how deeply divided state leaders remain over the budget for the coming fiscal year that begins on Thursday.

The exchange underscored concerns, which Bush Administration officials have privately expressed, that terrorists could eventually strike around the Middle East in support of Iraq.

But an exchange on Sunday's "Showtime" underscored his conflict.

But the exchange underscored the limits of NATO's military mission.

The exchanges underscored the marked divergence between Europe and the United States over how to approach Iran.

The exchanges underscored how not even the Thanksgiving holiday, typically a sort of national timeout, could defuse the intensity of this election struggle.