in tune with?

To be "in tune with the voters" here means, roughly, "aware of voters feelings and desires and responsive to them"

If you put two properly tuned pianos next to each other, or two guitars, and strike a key or pluck a string on one instrument, you may well hear the same note come from the other because sound waves cause a wire or string to vibrate "in sympathy". If this happens the two instruments are said to be "in tune" with each other.

contrex,
It is easy for me to understand the phrase better by knowing vibrating "in sympathy" in physics.We have just learnt it in the sciense class before.Thanks!

which means on the same frequency