After the war, Harper's Weekly more openly supported the Republican Party in its editorial positions, and contributed to the election of Ulysses S. Grant in 1868 and 1872.
It supported the Radical Republican position on Reconstruction.
In the 1870s, the cartoonist Thomas Nast began an aggressive campaign in the journal against the corrupt New York political leader William "Boss" Tweed.
Nast turned down a $500,000 bribe to end his attack.
Tweed was arrested in 1873 and convicted of fraud.

Nast and Harper's also played an important part in securing Rutherford B. Hayes' 1876 presidential election.
Later on Hayes remarked that Nast was "the most powerful, single-handed aid [he] had".
After the election, Nast's role in the magazine diminished considerably.
Since the late 1860s, Nast and George W. Curtis had frequently differed on political matters and particularly on the role of cartoons in political discourse.
Curtis believed that mockery by caricature should be reserved for Democrats, and did not approve of Nast's cartoons assailing Republicans such as Carl Schurz and Charles Sumner, who opposed policies of the Grant administration.
Harper's publisher Fletcher Harper strongly supported Nast in his disputes with Curtis.
In 1877, Harper died, and his nephews, Joseph W. Harper Jr. and John Henry Harper, assumed control of the magazine.
They were more sympathetic to Curtis' arguments for rejecting cartoons that contradicted his editorial positions.

In 1884, however, Curtis and Nast agreed that they could not support the Republican candidate James G. Blaine, whose association with corruption was anathema to them.
Instead they supported the Democratic candidate, Grover Cleveland.
Nast's cartoons helped Cleveland become the first Democrat to be elected president since 1856.
In the words of the artist's grandson, Thomas Nast St Hill, "it was generally conceded that Nast's support won Cleveland the small margin by which he was elected.
In his last national political campaign, Nast had, in fact, 'made a president.'"

Nast's final contribution to Harper's Weekly was his Christmas illustration in December 1886.
Journalist Henry Watterson said that "in quitting Harper's Weekly, Nast lost his forum: in losing him, Harper's Weekly lost its political importance."
Nast's biographer Fiona Deans Halloran says "the former is true to a certain extent, the latter unlikely.
Readers may have missed Nast's cartoons, but Harper's Weekly remained influential."
After the war, Harper's Weekly more openly supported the Republican Party in its editorial positions, and contributed to the election of Ulysses S. Grant in 1868 and 1872. It supported the Radical Republican position on Reconstruction. In the 1870s, the cartoonist Thomas Nast began an aggressive campaign in the journal against the corrupt New York political leader William "Boss" Tweed. Nast turned down a $500,000 bribe to end his attack. Tweed was arrested in 1873 and convicted of fraud.
Nast and Harper's also played an important part in securing Rutherford B. Hayes' 1876 presidential election. Later on Hayes remarked that Nast was "the most powerful, single-handed aid [he] had". After the election, Nast's role in the magazine diminished considerably. Since the late 1860s, Nast and George W. Curtis had frequently differed on political matters and particularly on the role of cartoons in political discourse. Curtis believed that mockery by caricature should be reserved for Democrats, and did not approve of Nast's cartoons assailing Republicans such as Carl Schurz and Charles Sumner, who opposed policies of the Grant administration. Harper's publisher Fletcher Harper strongly supported Nast in his disputes with Curtis. In 1877, Harper died, and his nephews, Joseph W. Harper Jr. and John Henry Harper, assumed control of the magazine. They were more sympathetic to Curtis' arguments for rejecting cartoons that contradicted his editorial positions.
In 1884, however, Curtis and Nast agreed that they could not support the Republican candidate James G. Blaine, whose association with corruption was anathema to them. Instead they supported the Democratic candidate, Grover Cleveland. Nast's cartoons helped Cleveland become the first Democrat to be elected president since 1856. In the words of the artist's grandson, Thomas Nast St Hill, "it was generally conceded that Nast's support won Cleveland the small margin by which he was elected. In his last national political campaign, Nast had, in fact, 'made a president.'"
Nast's final contribution to Harper's Weekly was his Christmas illustration in December 1886. Journalist Henry Watterson said that "in quitting Harper's Weekly, Nast lost his forum: in losing him, Harper's Weekly lost its political importance." Nast's biographer Fiona Deans Halloran says "the former is true to a certain extent, the latter unlikely. Readers may have missed Nast's cartoons, but Harper's Weekly remained influential."
Harper's Weekly