Minton went overseas to serve as a captain in the infantry during World War I. After practicing law in New Albany for several years, he was elected to the U.S. Senate from Indiana in the 1934 Democratic landslide. He was active in Democratic machine politics (the so-called McNutt machine), serving as a state commissioner of insurance. His success at saving Indiana citizens millions of dollars was an important factor in his election to the U.S. Senate.
Minton served in the U.S. Senate from 1935 until 1940. A staunch Democrat, he was a close ally of President Franklin Delano Roosevelt. Minton faithfully supported the New Deal and Roosevelt's “court-packing” plan, stands which cost him reelection in traditionally Republican Indiana in 1940.
While a senator, Minton attempted to circumvent the Constitution and to stifle criticism of the New Deal. He tried to make it unlawful to transport anti-New Deal literature in interstate commerce.
Upon arrival at the Senate, he was seated next to fellow freshman Senator Harry S Truman, with whom he formed a life-long friendship. Minton rose to the leadership positions of Deputy Whip and subsequently Whip, a unique accomplishment for a freshman senator.
The New York Times said of Minton's appointment that Truman had allowed personal and political friendship to influence his choice.
On the Court, Minton took a broad view of governmental powers, dissenting in Youngstown Sheet & Tube Co. v. Sawyer (1952), which ruled unconstitutional President Truman's wartime seizure of the steel mills in order to avert a strike. He disappointed liberals by voting to uphold anti-communist legislation during the period of the "red scare," voting with the majority in 1951's Dennis v. United States to uphold the conviction of the leader of the U.S. Communist Party.
Much of his judicial philosophy revolved around attempting to ascertain and uphold the original congressional intent behind legislation. However, Minton abhorred racial segregation and provided a solid vote to strike down the school segregation practices at issue in 1954's Brown v. Board of Education.
Minton consistently voted in favor of order at the cost of liberty. He was unsympathetic to challenges asserting violations of individual liberties. For example, in the 1949 case of United States v. Rabinowitz, Minton authored a 5-3 opinion declaring that warrantless searches were constitutional when incidental to a lawful arrest.
A lawyer writing for the New Jersey Law Journal labeled Minton a "spokesman against freedom," calling him "a man of conspicuous judicial shortcomings, whose votes against civil liberties exceeded those of any other man on the Court, and who wrote comparatively few opinions of other kinds.
The gregarious, backslapping Minton was popular among his colleagues on the Court, as he proved a soothing presence during a period on the Court marked by bitter personal feuds between strong personalities such as William O. Douglas and Felix Frankfurter. Minton did not make a jurisprudential mark on the Court. However, he and Truman's other appointees to the Court did provide consistent conservative votes, for a time returning the Court to the conservatism of the Taft era. He served as a Justice until October 15 1956, when he retired from the Court for reasons of ill health, particularly the effects of pernicious anemia, which he indicated had slowed him down both physically and mentally. Minton did not particularly enjoy his judgeship.
While on the court, he transformed from a New Deal senator into an almost reactionary judge under the influence of Justice Frankfurter. Empirical coding of votes shows that Minton was the most conservative justice on the Court during his first term there, and remained in the most conservative half of the court for the duration of his career.
For several years after retiring from the Supreme Court, Minton occasionally accepted assignments to serve temporarily on one of the lower federal courts. He regretted retiring from the Supreme Court almost immediately after going through with it. However, upon announcing his departure, he remarked: "There will be more interest in who will succeed me than in my passing. I'm an echo.
Minton retired from the Supreme Court only a month before its traditional opening, which rushed the process to find a replacement. President Eisenhower appointed Minton's replacement, Justice William Brennan, thinking him to be more conservative than he really was, in part because of this hurry.
Since Minton's retirement, there have been no other justices who also served previously in the legislative branch of the U.S. government.