Purchase — the Other Use (not Buying)

Not the usual use of the word when describing buying something. The word is used to describe a politician getting traction in his or her campaign or a train getting friction, torque and traction on the rails of a railroad.

Definition 2 a hold or position on something for applying power advantageously, or the advantage gained by such application : the horse’s hooves fought for purchase on the slippery pavement | [in sing. ] an attempt to gain a purchase on the soft earth.