run away with the idea
To take a fantastical or unrealistic idea as something that is definitely true or destined to happen. His book appeared on a local bestseller list, and now he's run away with the idea of being a famous author. Local tabloids are running away with the idea of the mayor being a part of a big conspiracy.
run away with the notion
To take a fantastical or unrealistic idea as something that is definitely true or destined to happen. His book appeared on a local bestseller list, and now he's run away with the notion of being a famous author. Local tabloids are running away with the notion of the mayor being a part of a big conspiracy.