By fall 1999 and early 2000, the Serbian opposition political parties, most notably the Democratic Party and the Serbian Renewal Movement (SPO), realized the potency of Otpor's methods and the resonance of its message with the youth. Thus began the battle for control of Otpor between DS and SPO. Since both parties already had a significant number of their youth wing members within Otpor, this trend continued on a large scale with both DS and SPO (and other opposition parties as well) instructing their local chapters throughout Serbia to recruit party youth members en masse into Otpor. As a result, Otpor's membership swelled into tens of thousands.