In 1868, McCrary successfully sought a U.S. House seat from
Iowa's 1st congressional district to succeed
Radical Republican James F. Wilson. He was elected as a
Republican from the district to the
United States House of Representatives of the
41st United States Congress and to the three succeeding Congresses, serving from March 4, 1869, to March 3, 1877. He was Chairman of the Committee on Elections for the
42nd United States Congress and Chairman of the Committee on Railways and Canals for the
43rd United States Congress. He published
A Treatise on the American Law of Elections, in 1875. In the
44th United States Congress, as a member of the
United States House Committee on the Judiciary, he was the author of a farsighted (but unsuccessful) bill to reorganize the federal courts to enable reasonable and prompt judicial review. He helped create the Electoral Commission to resolve the outcome of the
1876 Presidential Election, and served on the committee that investigated the
Crédit Mobilier scandal. He published
A Treatise on the American Law of Elections in 1875, which later underwent four editions. During his House years, McCrary allied with the congressional "
Half-Breeds," the loosely organized and more
moderate wing of the Republican Party (in comparison to the pro-
spoils system Stalwarts) which emphasized industrial interests and protective
tariffs in addition to supporting
civil service reform. ==Secretary of War==