On the formation of the Republican party, pledged to the restriction of the slave power, Judge Spalding took an active part in carrying out the principles of that organization. He was a member of the Pittsburgh Convention of 1856, at which the party was organized, and was a delegate at large for the State of Ohio at the Philadelphia Convention that nominated John C. Fremont. From that time he labored earnestly for the success of Republican principles, and the good effect of his efforts were frequently acknowledged by the party. In October, 1862, he was chosen to succeed Mr. Riddle as Representative of the Eighteenth Congressional District in Congress. The wisdom of the choice was almost immediately made manifest. Judge Spalding had not long occupied his seat in the House of Representatives before "the member from the Cleveland District" became noticed for the interest he took in questions of importance, the soundness of his views, and the ability with which they were urged. He took part in all the leading debates, and with such effect that he commanded the attention of the House whenever he spoke, and the leaders listened respectfully to his suggestions. He was appointed a member of the Standing Committee on Naval Affairs, and of the Committee on Revolutionary Pensions, and on the formation of a Select Committee on the Bankrupt Law, he was made its Chairman. In committee he was noticeable for his punctuality, patient and conscientious attention to the drudgery of committee work, and the system with which he was enabled to despatch large amounts of it satisfactorily. In 1864, he was re-elected to his seat, and in that term was made a member of the Standing Committee on Appropriations, and retained his former position on the Committee on Bankruptcy, the chairmanship of which was held by Mr. Jenckes. In this Congress Judge Spalding took a leading part in the important debates on the subject of Reconstruction, and impressed his influence on the Legislation upon this matter. In the early days of the session he made a speech, in which he indicated the measures he regarded best adapted for the for the purpose of properly reconstructing the rebel States. The speech attracted great attention, both within and without Congress, and the suggestions therein contained were for the most part subsequently adopted, and worked into the Reconstruction Laws. The military features of Reconstruction, which formed an integral part of the legislation, originated in an amendment proposed by Judge Spalding, when the first Reconstruction Bill of Thaddeus Stevens was presented.