He was first elected to the House of Commons as the representative for Kenora—Rainy River in 1988, beating NDP incumbent John Parry. Nault served as Minister of Indian Affairs and Northern Development in the cabinet of Jean Chrétien from 1999 to 2003. He introduced a comprehensive program of reform and financial accountability measures for First Nations.
After his first stint in the house of commons, Nault provided advisory and consulting services to high-technology firms, First Nations, and major public sector organizations.
In January 2015, Nault announced his intention to seek the Liberal Party of Canada nomination for Kenora, which includes nearly all of his old riding, in the 2015 federal election scheduled for October 19. In the ensuing election, he edged out provincial NDP leader Howard Hampton, who had represented the area provincially from 1987 to 2011, by only 2% to return to Parliament after a 12-year absence.
Incumbent Conservative and cabinet minister Greg Rickford was pushed into a distant third place.