What ads are political? Twitter struggles with a definition

The Alzheimer’s Association, a health care advocacy group, recently spent $84,000 on ad campaigns on Twitter. One campaign had a singular purpose: To persuade people to ask Congress for larger investments in medical research for the disease.

Now the nonprofit is worried about whether those messages will still fly. That’s because Twitter announced last month that it would soon prohibit all political ads from its platform — and, depending on whom you ask, pushing lawmakers for money for medical research could be seen as a political cause.