a question mark over something
1. if there is a question mark over something, no one knows whether it will continue to exist in the future or what will happen to it Neither company has performed well over the last year and there's a question mark over their long-term survival. A question mark hangs over the future of the whole project.
2. a feeling of doubt about the ability or quality of something The recent spate of government scandals has left a question mark over their ability to govern.