hot button

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Something that elicits a strong emotional response or reaction.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun idiomatic a central issue, concern or characteristic, especially one that motivates people to make a choice
• noun idiomatic, marketing the principal desire that a salesman needs to "hit" in order to make a sale