Tensions between the presumptive presidential nominees escalated over Sen. Barack Obama's refusal of public funds and Sen. John McCain's call to lift a ban on offshore drilling. Mark Shields and David Brooks discuss the political news of the week.

To combat rising fuel prices and other economic woes, Delta and Northwest airlines have agreed to a merger that would create the planet's biggest carrier, a move that could prompt similar proposals in the troubled industry.

By PBS NewsHour