play into someone's hands
Act in such a way as unintentionally to give someone an advantage: overreaction to the threats would be playing into the hands of the terrorists...- Half way through the third race there was no way I thought I would win but suddenly everything started playing into my hands and I took advantage.
- Most drivers and team engineers believe that Ferrari's advantage was exaggerated because the cool weather in Melbourne played into their hands.
- I fear I may already be playing into their hands by writing this and giving them more publicity, but I couldn't be silent.
See parent entry: play