hot potato 
noun informal
A controversial issue or situation which is awkward to deal with: dog registration has become a political hot potato...
- The play deals with the hot potatoes of race, madness and power and dazzles with a story as funny as it is provocative.
- The issue has been a hot potato on my radio show this week.
- The issue has become a political hot potato for Bloomberg, who faces a tough battle for re-election next year.