Harper was the first Canadian Prime Minister to come from the modern Conservative Party of Canada, which was formed by a merger of the Progressive Conservative Party and the Canadian Alliance. Harper was elected to the House of Commons of Canada for the riding of Calgary Southwest in Alberta from 2002 to 2015 and for Calgary Heritage until 2016. Earlier, from 1993 to 1997, he was the federal MP for Calgary West, representing the Reform Party of Canada. He was one of the founding members of the Reform Party, but did not seek re-election in the 1997 federal election. Harper instead joined and later led the National Citizens Coalition, a conservative lobbyist group. In 2002, he succeeded Stockwell Day as leader of the Canadian Alliance, the successor to the Reform Party and returned to parliament as Leader of the Opposition. In 2003, he reached an agreement with Progressive Conservative leader Peter MacKay for the merger of their two parties to form the Conservative Party of Canada. He was elected as the party's first leader, in March 2004.