Is it wrong?

This is stemming from a poll I saw so it isn’t personal experience but is it wrong to be happily committed to someone and develop a crush on someone else? Majority of the poll answered no that it’s not wrong, but no one commented, so it got me curious. In my brain, when I hear “crush” it’s someone you don’t talk to often but find attractive, or maybe flirt with but not too much ?? I’m not sure. Thoughts?