high wire-act

A risky job or operation, as in

The university press is not allowed to either make or lose money--that's a high-wire act.

From a report delivered by Andrea Mitchell of NBC Nightly News, July 18, 2008.

Ann, Barack Obama is coming here because he knows that many voters still doubt his ability to be commander-in-chief. But taking such a high profile foreign tour also carries somewhat of high wire-act.