Being a member of the Supreme Party Council of BSP, he declared himself openly against the party in 2005 by not supporting BSP Mayor of Sofia candidate Tatyana Doncheva and instead favouring the independent Boyko Borisov. Because of this he was taken down from the post of BSP municipal councillors leader in Sofia. Before the 2009 Bulgarian parliamentary election, Dimitrov formally left BSP and joined Borisov's GERB. He was the party's candidate for 2nd MMC – Burgas in the first-past-the-post vote and won the election with 35.92%. He finished ahead of Volen Siderov, the leader of the nationalist Attaka.