After serving as a county judge, Truman wanted to run for Governor or Congress, but Pendergast rejected these ideas.
Truman then thought he might serve out his career in some well-paying county sinecure; circumstances changed when Pendergast reluctantly backed him as the machine's choice in the 1934 Democratic primary for the U.S. Senate from Missouri, after Pendergast's first four choices had declined to run.
In the primary, Truman defeated Congressmen John J. Cochran and Jacob L. Milligan with the solid support of Jackson County, which was crucial to his candidacy.
Also critical were the contacts he had made statewide in his capacity as a county official, member of the Masons, military reservist, and member of the American Legion.
In the general election, Truman defeated incumbent Republican Roscoe C. Patterson by nearly 20 percentage points in a continuing wave of pro-New Deal Democrats elected following the Great Depression.

Truman assumed office with a reputation as "the Senator from Pendergast".
He referred patronage decisions to Pendergast, but maintained that he voted with his own conscience.
He later defended the patronage decisions by saying that "by offering a little to the machine, [he] saved a lot".
In his first term, Truman spoke out against corporate greed and the dangers of Wall Street speculators and other moneyed special interests attaining too much influence in national affairs.
Though he served on the high-profile Appropriations and Interstate Commerce Committees, he was largely ignored by Democratic President Roosevelt and had trouble getting calls returned from the White House.

During the U.S. Senate election in 1940, United States Attorney Maurice Milligan (Jacob Milligan's brother) and former governor Lloyd Stark both challenged Truman in the Democratic primary.
Truman was politically weakened by Pendergast's imprisonment for income tax evasion the previous year; the senator had remained loyal, having claimed that Republican judges (not the Roosevelt administration) were responsible for the boss's downfall.
St. Louis party leader Robert E. Hannegan's support of Truman proved crucial; he later brokered the deal that put Truman on the national ticket.
In the end, Stark and Milligan split the anti-Pendergast vote in the Senate Democratic primary and Truman won by a total of 8,000 votes.
In the November election, Truman defeated Republican Manvel H. Davis by 51–49 percent.
As Senator, Truman opposed both Nazi Germany and Communist Russia.
One week after Hitler invaded the Soviet Union in 1941, he said:
If we see that Germany is winning we ought to help Russia, and if Russia is winning we ought to help Germany, and that way let them kill as many as possible although I don't want to see Hitler victorious under any circumstances.
After serving as a county judge, Truman wanted to run for Governor or Congress, but Pendergast rejected these ideas. Truman then thought he might serve out his career in some well-paying county sinecure; circumstances changed when Pendergast reluctantly backed him as the machine's choice in the 1934 Democratic primary for the U.S. Senate from Missouri, after Pendergast's first four choices had declined to run. In the primary, Truman defeated Congressmen John J. Cochran and Jacob L. Milligan with the solid support of Jackson County, which was crucial to his candidacy. Also critical were the contacts he had made statewide in his capacity as a county official, member of the Masons, military reservist, and member of the American Legion. In the general election, Truman defeated incumbent Republican Roscoe C. Patterson by nearly 20 percentage points in a continuing wave of pro-New Deal Democrats elected following the Great Depression.
Truman assumed office with a reputation as "the Senator from Pendergast". He referred patronage decisions to Pendergast, but maintained that he voted with his own conscience. He later defended the patronage decisions by saying that "by offering a little to the machine, [he] saved a lot". In his first term, Truman spoke out against corporate greed and the dangers of Wall Street speculators and other moneyed special interests attaining too much influence in national affairs. Though he served on the high-profile Appropriations and Interstate Commerce Committees, he was largely ignored by Democratic President Roosevelt and had trouble getting calls returned from the White House.
During the U.S. Senate election in 1940, United States Attorney Maurice Milligan (Jacob Milligan's brother) and former governor Lloyd Stark both challenged Truman in the Democratic primary. Truman was politically weakened by Pendergast's imprisonment for income tax evasion the previous year; the senator had remained loyal, having claimed that Republican judges (not the Roosevelt administration) were responsible for the boss's downfall. St. Louis party leader Robert E. Hannegan's support of Truman proved crucial; he later brokered the deal that put Truman on the national ticket. In the end, Stark and Milligan split the anti-Pendergast vote in the Senate Democratic primary and Truman won by a total of 8,000 votes. In the November election, Truman defeated Republican Manvel H. Davis by 51–49 percent. As Senator, Truman opposed both Nazi Germany and Communist Russia. One week after Hitler invaded the Soviet Union in 1941, he said:
If we see that Germany is winning we ought to help Russia, and if Russia is winning we ought to help Germany, and that way let them kill as many as possible although I don't want to see Hitler victorious under any circumstances.
Harry S. Truman