Senator Kay Hagan surveyed damage from Hurricane Irene this week on the eastern shore of North Carolina. She wore a white shirt:
This crisp button-down shirt paired with dark slacks is a bit more formal than Senator Landrieu's polo shirts, but still appropriate for the situation, provided you have access to an iron. She looks authoritative while also having literally rolled up her sleeves in a messy situation.
I would have perhaps not chosen such large earrings, though. Imagine a disaster area is like a baby - you might lose anything that's dangling or delicate.