Franklin Roosevelt began his political career in 1910 when he won a seat in the New York State Senate. He rose quickly from that post to become a prominent national figure, helped in part by his family name.
After only two years as a state senator, Roosevelt was appointed assistant secretary of the Navy in Woodrow Wilson's first administration. He used this post to make himself well-known and well-connected in Democratic circles. This led to him being chosen as the vice presidential candidate in the 1920 election (which the Democrats lost).
After being paralyzed by polio in 1921, Roosevelt did not hold office for some time. However, he remained active in the Democratic Party. He won election as the governor of New York in 1928 and was seen as the most likely presidential candidate for 1932. When the Depression hit, his path to the presidency was made easier. President Hoover became so unpopular due to the Depression that it was relatively easy for Roosevelt to rise to the presidency.