Blaine was born on January 31, 1830 in the western Pennsylvania town of West Brownsville, the son of a wealthy businessman and landowner. After college he moved to Maine where his wife Harriet was from and where he became a newspaper editor. He was nicknamed "the Magnetic Man" because he was a charismatic speaker in an era that prized oratory. He began his political career as an early supporter of Abraham Lincoln and the Union war effort in the American Civil War. In Reconstruction, Blaine was a supporter of voting rights for African-Americans, but opposed some of the more radical measures of the group known as the Radical Republicans. Initially a protectionist, he later worked for a reduction in the tariff and an expansion of American trade with foreign countries. Railroad promotion and construction were important issues in his time, and as a result of his interest and support Blaine was widely suspected of corruption in the awarding of railroad charters. These allegations plagued his 1884 presidential candidacy.
Blaine sought his party's nomination for President in 1876, but a split in the party between Blaine's "half-breeds" (so named because their opponents said that they were only half Republican) and Roscoe Conkling's Stalwart faction resulted in a compromise candidate being nominated - Governor Rutherford Hayes of Ohio. He tried again in 1880, but this time the Stalwart candidate was former President Ulysses Grant. Once again the Republicans compromised and selected another Ohio politician: Congressman James Garfield. When Garfield was elected President, he chose Blaine as his Secretary of State to balance off the fact that he had chosen a Stalwart as his running mate (Chester Alan Arthur).
As Secretary of State, Blaine was a transitional figure. He ended an isolationist era in foreign policy, foreshadowing the rise of the American Century that would begin with the Spanish-American War. His efforts at expanding the United States' trade and influence began the shift to a more active American foreign policy. Blaine was a pioneer of tariff reciprocity and urged greater involvement in Latin American affairs. An expansionist, Blaine's policies would create a climate conducive to the establishment of the acquisition of Pacific colonies.
In 1884 Blaine was able to gather enough momentum to win his party's nomination for President. Democrats nominated New York Governor Grover Cleveland and hoped that their candidate's reputation as a reformer and an opponent of corruption would attract Republicans dissatisfied with Blaine. They were correct, as reform-minded Republicans (called "Mugwumps") denounced Blaine as corrupt and flocked to Cleveland. Cleveland's supporters rehashed the old allegations that Blaine had corruptly influenced legislation in favor of railroads, later profiting on the sale of bonds he owned in both companies. Although the stories of Blaine's favors to the railroads were eight years old, this was still an Achilles heal for Blaine. What Blaine called "stale slander" served to focus the public's attention negatively on his character. The rallying cry of Democrats was "Blaine, Blaine, James G. Blaine, the continental liar from the state of Maine!"
In New York, Blaine received less support than he anticipated when Arthur and Conkling, still powerful in the New York Republican party, failed to actively campaign for him. Cleveland narrowly won all of the swing states, including New York by just over one thousand votes. While the popular vote total was close, with Cleveland winning by just one-quarter of a percent, the electoral votes gave Cleveland a majority of 219–182. If the Stalwart faction had worked for Blaine's election, he might have won New York and with it the presidency.
Blaine spent the years following his defeat traveling to Europe as some urged him to run against Cleveland in a rematch. He supported Benjamin Harrison in the election of 1888 and was selected as Secretary of State in Harrison's cabinet. But the relationship between the two men wasn't a good one. Harrison was aware that his Secretary of State was more popular than he was, and while he admired Blaine's gift for diplomacy, he grew displeased with Blaine's frequent absence from his post because of illness, and suspected that Blaine was angling for the presidential nomination in 1892.
Blaine's health was in fact fragile by the time he joined Harrison's cabinet. This was compounded by personal tragedy as two of his children, Walker and Alice, died suddenly in 1890. Another son, Emmons, died in 1892. With these family issues and his declining health, Blaine decided to retire and announced that he would resign from the cabinet on June 4, 1892. Harrison was unpopular with the party and the country, and many of Blaine's old supporters encouraged him to run for the nomination. When Blaine resigned from the cabinet, his boosters were certain that he was a candidate, but the majority of the party stood by the incumbent. Harrison was renominated on the first ballot, but die-hard Blaine delegates still gave their champion 182 and 1/6 votes, good enough for second place.
Blaine spent the summer of 1892 at his Bar Harbor cottage, and did not involve himself in the presidential campaign other than to make a single speech in New York in October. Harrison was defeated soundly in his rematch against former president Cleveland and when Blaine returned to Washington at the close of 1892, he and Harrison seemed to patch up their differences. Blaine's health declined rapidly in the winter of 1892–1893, and he died in his Washington home on January 27, 1893. After a funeral at the Presbyterian Church of the Covenant, he was buried in Oak Hill Cemetery in Washington. He was later re-interred in Blaine Memorial Park, Augusta, Maine, in 1920. Historian R. Hal Williams of SMU is currently working on a new biography of Blaine, tentatively titled James G. Blaine: A Life in Politics.