hot button 
noun [often as modifier] North American informal
A topic or issue that is highly charged emotionally or politically: the hot-button issue of nuclear waste disposal...
- Crime is the hot button issue of modern politics, generating more heat than any other topic.
- Even on the hot button issue of crime, the Democrats managed to pull even in the last decade.
- People don't think that politics can be absolutely hilarious, and getting involved politically doesn't have to be about arguing about hot button issues.