He was successful in defending organized labor and as a defense counsel in high-profile murder cases, where he used his popularity to run for office.

In 1930, he was elected to New Mexico's one at-large seat in the United States House of Representatives as a Democrat, and was re-elected in 1932.

However, Cutting was killed in an airplane crash on May 6, 1935, and five days later, Chávez was appointed to fill the vacancy pending a special election.

A resolution that claimed no candidate had won the 1952 election, and therefore requiring the Republican governor of New Mexico to appoint a new senator, was defeated by a vote of 36-53.

Dennis Chávez died of cancer, attributed to his being a lifelong smoker, in Washington, D.C., on November 18, 1962,[5] and was buried at Mount Calvary Cemetery in Albuquerque, New Mexico.

Congress honored his memory with a minute of silence, and then-Vice-President Lyndon B. Johnson spoke at his funeral.

[citation needed] He was honored by the United States Postal Service with a 35¢ Great Americans series (1980–2000) postage stamp.

"[6] A granddaughter, Gloria Tristani, followed in public service, serving as chair of the New Mexico State Corporations Commission in 1996, as a member of the Federal Communications Commission from 1997 to 2001, and as the Democratic nominee for New Mexico's other U.S. Senate seat in 2002 where she lost to Senator Pete Domenici.