Are you applying for any other jobs?

"I am passively looking for a job at this time. In my current role, I am satisfied, but am keeping an eye out for future growth opportunities. Your position certainly caught my eye."

It always puts a little bit of fire under the hiring manager if they are aware that you are actively looking for a new position. Tell the interviewer about your search so far.

"I am keeping an eye out for viable positions. Although I am not in final stages with any other company, I am actively seeking a new position."

Community answers are written by other candidates practicing this set. Reading how others frame the same question is one of the fastest ways to sharpen your own.