As one of the founding members of the Reform Party, he ended his first stint as an MP to head the National Citizens Coalition. After the ousting of leader Stockwell Day in 2002, Harper became leader of the Canadian Alliance and returned to Parliament. In 2003, he successfully reached an agreement with Progressive Conservative leader Peter MacKay to merge the Canadian Alliance with the Progressive Conservative Party to form the Conservative Party of Canada. He was elected as the new party's first leader in March 2004. He led the Conservatives to a minority government win in the January 2006 federal election.
He first became involved in politics in high school, serving as a member of the school's Young Liberals Club. However, Harper's political allegiance later changed in opposition to the Trudeau Liberal government's National Energy Program (NEP), which he thought was harming Alberta's energy industry. He became chief aide to Tory MP Jim Hawkes in 1985, but quickly became disillusioned with the government of Brian Mulroney and the Progressive Conservative (PC) Party. Harper was especially critical of the government's fiscal policy and inability to fully revoke the NEP until 1986. He left the PC Party in 1986.
On January 12, 2004, Harper announced his resignation as Leader of the Opposition, in order to run for the leadership of the Conservative Party of Canada. Harper won the Conservative leadership election easily, with a first ballot majority against Belinda Stronach and Tony Clement on March 20, 2004. Harper's victory included strong showings in Ontario, Quebec, and Atlantic Canada.
Harper started off the first month of the campaign with a policy-per-day strategy, which included a GST reduction and a child-care allowance. The Liberals opted to hold any major announcements until after the Christmas holidays; as a result, Harper dominated media coverage for the first weeks of the campaign and was able to define his platform and insulate it from expected Liberal attacks. Though his party showed only modest movement in the polls, Harper's personal numbers, which had always trailed his party's significantly, began to rise.
On December 27, 2005, the Royal Canadian Mounted Police announced it was investigating allegations that Liberal Finance Minister Ralph Goodale's office had engaged in insider trading before making an important announcement on the taxation of income trusts. The income trust scandal dominated news coverage for the following week and prevented the Liberals from making their key policy announcements, allowing Harper to refocus his previous attacks about corruption within the Liberal party. The Conservatives soon found themselves leading in the polls. By early January, they even made a major breakthrough in Quebec, pushing the Liberals to second place.
On January 23, the Conservatives won 124 seats against 103 for the Liberals. Martin conceded defeat at midnight on January 24, and at 9:45 a.m. that morning, announced his intention to resign as Prime Minister. At 6:45 p.m., Governor General MichaŽlle Jean asked Harper to form a government. He was sworn in as Canada's 22nd Prime Minister on February 6, 2006. Harper is the first Prime Minister elected to office not representing a Quebec riding since Joe Clark in 1979.