走内线

Traditional (Taiwan): 走內線

zǒunèixiàn ㄗㄡˇ ㄋㄟˋ ㄒㄧㄢˋ

    • insider contacts
    • via private channels
    • to seek influence with sb via family members (possibly dishonest or underhand)

Character by character

Saying俗语俗語

Idiom惯用语 · Widely known

Literally
work the inside line
Meaning
Either to act through a spy planted in the other side, or to seek favours through the relatives and confidants of someone in power.

Sources