third rail

US /ˌθɜːrd ˈreɪl/
UK /ˌθɜːrd ˈreɪl/
"third rail" picture
1.

dritte Schiene, heikles Thema

a political issue that is so controversial that any politician who dares to broach the topic will suffer a backlash from voters

:
Healthcare reform has become a third rail issue in American politics.
Die Gesundheitsreform ist in der amerikanischen Politik zu einem heiklen Thema geworden.
No politician wants to touch the third rail of social security.
Kein Politiker will das heikle Thema der Sozialversicherung anfassen.