Hamada contested the Tottori at-large district of the national House of Councillors at the July 2010 election as a candidate for the Liberal Democratic Party. He won the seat with 50.2% percent of the vote and defeated the Democratic Party of Japan candidate Mari Sakano, the granddaughter of Shigenobu Sakano, a former LDP member who had held the seat from 1986 until his death in April 2002. On 27 June 2011, whilst still a member of the opposition LDP, Hamada was offered a position in the government of Naoto Kan as Vice-Minister for Internal Affairs and Communications. The position would see Hamada be responsible for recovery efforts arising from the March 2011 Tōhoku earthquake and tsunami. He resigned from the LDP and joined the ministry the following day. The LDP responded to the move a week later by rejecting his resignation and instead expelling him from the party. He sat as an independent for several months before joining the People's New Party on 29 December 2011. In September 2011 Kan was replaced as prime minister by Yoshihiko Noda. Hamada became a Vice-Minister for Foreign Affairs in Noda's cabinet and remained in the position until the DPJ were defeated by the LDP in the December 2012 general election. The People's New Party also performed poorly in the election, and in the aftermath Hamada became Secretary-General of the party. By March 2013 he and party leader Shozaburo Jimi were the only party members remaining in the Diet and they decided to disband the party. Whilst again sitting as an independent, he caused some controversy in April 2014 during United States PresidentBarack Obama's state visit to Japan by claiming that Michelle Obama's absence from the visit was evidence that the couple were "negotiating a divorce". Hamada joined the Party for Future Generations in November 2014, which changed its name to the Party for Japanese Kokoro in December 2015. From the same time Hamada served as the party's Diet leader.
2016 re-election campaign
In April 2016 Hamada resigned from the Party for Japanese Kokoro and joined Initiatives from Osaka. Hamada's Tottori constituency was to be merged with the Shimane at-large district to create the Tottori-Shimane at-large district and contesting the new seat as a minor party candidate against Kazuhiko Aoki, the LDP's incumbent member for Shimane, would prove too difficult. Instead Hamada received a nomination to contest the summer 2016 election from the national proportional representation block as an Initiatives from Osaka candidate. However, on Friday 27 May 2016 Hamada caused controversy when he was absent from the House of Councillors, which was debating bills related to relief following the 2016 Kumamoto earthquakes, in order to attend a party meeting in Osaka for Osaka prefectural representatives. He greeted the meeting by saying "I have come today to say a greeting to the all-star cast in attendance". His attendance was intended to gain support within the party for his national block campaign, and Hamada later explained that he had the party's permission to be absent from the House debate. However, the party's leader in the Osaka Prefectural Assembly, Kazunori Ohashi, said the party was unaware of his intended absence. On the following Monday, party secretary-general announced that the party had removed Hamada as a candidate, saying that his absence from the House in order to progress his re-election campaign was "extremely regrettable". Hamada submitted his resignation to the party on the same day, which was accepted the following day, 1 June 2016. Hamada nominated for the July House of Councillors election as an independent candidate in the six-seat Tokyo at-large district. He came 16th in a field of 31 candidates, receiving just 0.5% of the vote. Meanwhile, Aoki won the merged Tottori-Shimane district with 62.7% of the vote in a three-candidate race.
