Career in national politics
Heinäluoma was elected chairman in June 2005, succeeding former Prime Minister Paavo Lipponen. He was the Minister of Finance of Finland from 2005 to 2007.
Heinäluoma held various posts in the Central Organisation of Finnish Trade Unions (SAK) from 1983 to 2003. He was a director in SAK from 2000 to 2003. Heinäluoma was appointed as party secretary in 2002 and in the 2003 elections, he was elected as a Member of Parliament from the Electoral District of Uusimaa. Ever since he took up the post of Party secretary, he had, according to many, been groomed as Lipponen's heir.
He won on the first ballot, getting 201 of 350 votes. His rivals were Foreign Minister Erkki Tuomioja, with 138 votes, and Minister of Education Tuula Haatainen, with 11 votes.
As party chairman, Heinäluoma ordered a reshuffle of SDP cabinet ministers and assumed the position of Minister of Finance on 23 September 2005. In the 2007 elections, the party led by Heinäluoma suffered a significant loss, losing 15% of their seats in the parliament, and having the worst result since 1962. The loss led to the resignation of Heinäluoma as the party chairman.
Heinäluoma was elected as the chairman of the Social Democratic parliamentary group in February 2010 and served in that position until becoming Speaker in June 2011.
In June 2016, Heinäluoma announced that he would not become his party's candidate for the 2018 presidential election due to his wife's recent death.