Carr first ran as a Democrat for Michigan's 6th congressional district in 1972, facing eight-term Republican incumbent Charles E. Chamberlain. Chamberlain only narrowly defeated Carr by 97,666 votes to 95,029 in what was otherwise a strong Republican year, which persuaded Chamberlain to retire in 1974, when he was succeeded by Carr. Carr represented the district in the U.S. House for the 94th and to the two succeeding Congresses, serving from January 3, 1975 to January 3, 1981. He was an unsuccessful candidate for re-election in 1980 to the 97th Congress, being defeated by James Whitney Dunn. Two years later, he defeated Dunn and was elected to the 98th and subsequently re-elected to the five succeeding Congresses, serving from January 3, 1983 to January 3, 1995. The last two years he represented Michigan's 8th congressional district after the redistricting in 1993. He was not a candidate for re-election in 1994, but was an unsuccessful candidate for election to the United States Senate, losing to Spencer Abraham. Carr began his career in Congress with a reputation as a rebel and self-described "angry young man." Shortly after his election in 1974, he called for the resignation of Democratic U.S. House Speaker Carl Albert. Carr later expressed public regret for his early attacks on the Congressional leadership and called them "sheer, naive stupidity." After taking office in 1975 Carr was named to the House Armed Services Committee, where he focused his attention on ending U.S. involvement in the war in Southeast Asia. On March 12, 1975 with the influential help of House Democratic Caucus ChairmanPhillip Burton, Carr authored a resolution that passed the Caucus by 189-49 effectively cutting off further military assistance to South Vietnam or to Cambodia in fiscal year 1975. After losing and regaining his seat in the 1980 and 1982 elections, respectively, he was named to the House Committee on Appropriations, lowered his profile and focused his attention on budget and spending issues. He became chairman of the Subcommittee on Transportation, where he pioneered the use of economic-based criteria and ranks to earmarks requested by members of Congress for their districts.
Later career
From 1995 to 2006 Carr worked as a consultant in international business and government affairs. From 2005 to 2012 he was Of Counsel at , a communications law firm in Washington, DC. In 2012 Carr became Adjunct Professor in at and adjunct faculty at Brookings Institution's Brookings Executive Education where he lectures on Congressional Appropriations, Authorization and Budgeting. He also assists in the Brookings Legislative Fellows program. In 2007 Carr was diagnosed with multiple myeloma and successfully underwent an autologous stem cell transplant at the Dana–Farber Cancer Institute in 2008. Since then he has been involved advocating for funding for cancer research and was featured in the . He is a member of the board of directors of the . Carr is also a member of the ReFormers Caucus of Issue One. Divorced, he has one child, Alexandra Anne, a stepdaughter Jennifer Smith McCloskey, and a stepson Christopher Smith McCloskey.