[4] Walsh became a leader in Democratic Party politics in Helena and attended numerous local, county and state conventions as a delegate.

He emerged as a spokesman for President Woodrow Wilson in the Senate and supported the graduated income tax, farm loans, and women's suffrage.

In the 1920s, Walsh headed the Senate investigation into the Teapot Dome scandal that involved top officials of the administration of President Warren G.

[6] The investigation done by the Federal Trade Commission would continue through 1935 and eventually result in four of the most important laws governing the electric industry in the 20th century including the breakup of most of the large holding companies that formed during the 1920s.

In late February, he secretly married wealthy Cuban widow Mina Nieves Perez Chaumont de Truffin in Havana, Cuba.

Less than a week later, he died while en route by train to Washington for Roosevelt's inauguration,[5] allegedly poisoned by his new wife.

[8] His funeral service was held in the Chamber of the United States Senate, and he was interred at Resurrection Cemetery in Helena.