Along with Chicago lawyer Harold L. Ickes, he launched a campaign against public utility tycoon Samuel Insull's stock market manipulations.

[citation needed] Working with the state legislature, he helped draft laws regulating utilities and establishing old-age pensions and unemployment insurance.

After Roosevelt's victory in the election, Douglas, at the recommendation of his friend Harold Ickes, was appointed to serve on the Consumers' Advisory Board of the National Recovery Administration.

That year, Douglas made his first foray into electoral politics, campaigning for the endorsement of the local Republican Party for mayor of Chicago.

During the municipal election cycle, Mayor Edward Joseph Kelly was challenged for re-election and attempted to shore up his reputation by lending his support to Douglas' campaign.

With the aid of Knox, Douglas enlisted in the United States Marine Corps on May 15, 1942, at the age of 50,[6] becoming the oldest recruit in the history of Parris Island.

[9] Initially, Douglas was kept stateside, writing training manuals and giving inspirational speeches to troops, and quickly rose to the rank of staff sergeant.

[12] On the second day of the battle, Captain Douglas received permission to head to the front where he found work as a mobile regimental troubleshooter.

A volunteer rifleman in an infantry platoon, he was helping to carry wounded from 3rd Battalion 5th Marines along the Naha-Shuri line when a burst of machine gun fire tore through his left arm, severing the main nerve and leaving it permanently disabled.

[14] After a thirteen-month stay in the National Naval Medical Center at Bethesda, Maryland, Douglas was given an honorable discharge as a lieutenant colonel with full disability pay.

I was disconcerted to find that the economic and political conservatives had acquired almost complete dominance over my department and taught that market decisions were always right and profit values the supreme ones ...

At the time, several scandals had broken out over the machine's activities, and Arvey decided that Douglas, a scholar and war hero with a reputation for incorruptibility, would be the perfect nominee to run against Senator Brooks.

Since Brooks was hugely popular in the state and had a large campaign warchest, Arvey decided that there was no danger of Douglas winning.

[citation needed] The top two thirds of the Illinois Democratic slate for the 1948 election then became Paul Douglas for senator and Adlai Stevenson for governor.

He stumped across the state in a Jeep station wagon for the Marshall Plan, civil rights, repeal of the Taft-Hartley Act, more public housing, and more social security programs.

As senator, Douglas soon earned a reputation as an unconventional liberal, concerned as much with fiscal discipline as with passing the Fair Deal.

At the opening of the 85th United States Congress in January 1957, a session that would see the passing of the Civil Rights Act of 1957 in September, Douglas was the only senator to defy custom and vote against the confirmation of segregationist James Eastland as the chairman of the Judiciary Committee.

When Maine's Owen Brewster objected and pointed out the millions of dollars in pork going to Illinois, Douglas offered to cut his state's share by 40%.

A profile of him in that issue was entitled “The Making of a Maverick.” Subsequently, as chair of the Joint Economic Committee, he led a series of hard-hitting investigations into fiscal mismanagement in government.

Douglas, however, refused to be considered as a candidate for president, instead backing the candidacy of Senator Estes Kefauver of Tennessee, a folksy, coonskin cap-wearing populist who had become famous for his televised investigations into organized crime.

Four years later, in 1956, he remained publicly neutral, feeling that openly opposing Stevenson's drive for the nomination and supporting Kefauver would damage his standing with his state party.

[citation needed] In addition to his battles for equal rights for African Americans and less pork barrel spending, Douglas was also known for his fights for environmental protection, public housing, and truth in lending laws.

[25] In his memoirs, Douglas perhaps jokingly asked Saint Paul to forgive him for his silence in the Senate on what he considered to be the important land values problem.

[26] Unlike some other liberals, Douglas was an opponent of a national health insurance program, claiming the Wagner-Murray-Dingell bill supported by President Harry Truman went too far.

[28] During the 1966 election, Douglas, then 74, ran for a fourth term in office against Republican Charles H. Percy, a wealthy businessman and former student of his.

After losing his seat in the Senate, Douglas taught at the New School, chaired a commission on housing, and wrote books, including an autobiography, In the Fullness of Time.