a hot button
a hot buttonAMERICAN, INFORMAL
COMMON If a subject or problem is a hot button, people have very strong feelings about it. If crime is the city's issue most known to outsiders, rent control is the city's hot button for its residents. Note: Hot-button can be used before a noun. These controversial, hot-button issues create hazards for politicians.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012