Defensor Santiago ran for senator in 2004 and was elected. She focused on creating significant laws that changed the country as a whole. She ran again for senator in 2010 and won. During her three terms, she served as chair mostly of the foreign relations committee and the constitutional amendments committee. She was elected as official candidate of her party People's Reform Party, serving also as chair of the Foreign Affairs Committee of the Commission on Appointments. She exposed and named numerous "jueteng" (illegal gambling) lords and illegal-logging lords throughout her terms.