SAN FRANCISCO — 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.

The Alzheimer’s Association was so concerned that it contacted Twitter this month to express misgivings about the political ads ban. “We’re not really sure how it’s going to impact us,” said Mike Lynch, a spokesman for the group. “A lot of what we do is issue advertising, so it really depends on how they define political advertising.”

The Alzheimer’s Association is one of many nonprofits and organizations that have put pressure on Twitter over its prohibition of political ads, which is set to start next Friday. The problem is that while campaign ads from candidates are clearly political, other messages that deal with hot-button issues such as abortion, school choice and climate change may or may not cross that line.