hold/have somebody in the palm of your hand
From Longman Dictionary of Contemporary Englishhold/have somebody in the palm of your handhold/have somebody in the palm of your handFORCE somebody TO DO somethingto have a strong influence on someone, so that they do what you want them to do → palmExamples from the Corpushold/have somebody in the palm of your hand• She's got the whole committee in the palm of her hand.