third rail
US /ˌθɜːrd ˈreɪl/
UK /ˌθɜːrd ˈreɪl/

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.