In 1987, Pahor his degree in political science with a focus on International Relations. From 1990 to 1992 he was a member of the Parliamentary Assembly of the Republic of Slovenia, from 1992 Member of the State Assembly from 2000 to 2004 its president. In the same year he was elected as a candidate of the democratic Socialni in the European Parliament, he was a member of the Group of the Party of European Socialists.
From 1997 he was chairman of the political party United List of Social Democrats (Slovenian Združena lista socialnih demokratov or ZLSD ) in Slovenia, he was Chairman of the products resulting from the ZLSD party Socialni democratic (SD) 2005.
On September 21, 2008, his party won with him as the leading candidate the parliamentary elections in Slovenia. He was elected by the National Assembly on 7 November 2008 as prime minister. His mandate in the European Parliament he resigned 14 October 2008, when substitutes pulled a Aurelio Juri.
Almost to the day exactly three years after the election, on 20 November 2011, the National Assembly, the first chamber of the Slovenian Parliament, the Government and the Prime Minister Pahor expressed distrust. Preceded the vote were several resignations of cabinet members. For outrage especially a corruption scandal had worried about the former Interior Minister Katarina Kresal. According to a survey conducted by the daily newspaper Dnevnik, 84 percent of the population were last dissatisfied with the work of the government.
Since the National Assembly had chosen a successor to Pahor, early parliamentary elections on 4 December 2011, proclaimed. Pahor's SD lost in the elections almost two thirds of its seats in parliament and became only the third strongest force in the new parliament. On January 28, 2012 Janez Janša was sworn in as the new Slovenian Prime Minister.
On December 2, 2012, Pahor added in the second round of the presidential election in Slovenia with 67.4 percent of the vote against the incumbent by Danilo Türk. The inauguration Pahor took place on 23 December 2012.
Activities as a member of the European Parliament
As a member of the European Parliament ( MEP ) Pahor was Deputy Chairman of the Delegation to the EU-Croatia Joint Parliamentary Committee and a member of the Committee on Budgetary Control, the Committee on Constitutional Affairs. Deputy member he was in the Committee on Foreign Affairs and the Temporary Committee on the alleged use of European countries by the CIA for the transportation and illegal detention of prisoners.