In addition to these children of their own, the couple helped raise several others: Charles, Abigail, and Rachel Clark, the children of Ewing's sister Rachel; Lewis Wolfley, whose father was Ewing's cousin; and, the most famous of all, William Tecumseh Sherman, who subsequently married Ewing's daughter Ellen and whose father, Charles R. Sherman, a judge of the Ohio Supreme Court, had died suddenly in 1829 leaving a widow and eleven children. A devoted family man, Ewing demonstrated a deep interest in both their education and their pastimes.
In 1823, he served as a member of a Committee appointed to revise the General Laws of Ohio. In the same year he also became a trustee of his alma mater, Ohio University, a post he held until 1832. Caught up in the canal building mania of the 1820's, he served as one of the seven commissioners, and for a brief period as President of the Board of Directors, of the Lancaster Lateral Canal Company. The young lawyer, like so many who followed the same profession, soon developed a taste for politics. Defeated in 1823 in a bid for a seat in the Ohio Legislature, for the next few years he devoted his attention to his law practice. However, in the Summer of 1827, he served as a delegate from Ohio to the Harrisburg Convention of Friends of Farming and Manufacturing which drew up a memorial requesting Congressional action to protect domestic industry. In December of the same year, he headed Fairfield County's delegation to the State Convention of Adams' Men at Columbus and served as a member of both the Resolutions Committee and the State Central Committee. Already recognized as a leader of the Ohio Bar, in January of 1828 he was admitted to practice before the United States Supreme Court, joining the company of such brilliant practitioners as Daniel Webster, Henry Clay, John C. Calhoun, and Robert Young Hayne.
In the Fall of 1830, he decided to stand as a candidate for United States Senator from Ohio. he was elected on the sixth ballot. On March 4, 1831, Tom Ewing, who in his only other quest for political office had been defeated in a bid for a seat in the Ohio Legislature, took his seat as a member of the Whig Party in the United States Senate. He served until March 3, 1837. Among the most active of his fellow Senators were: Daniel Webster, Henry Clay, John C. Calhoun, Robert Young Hayne, William Campbell Preston, James Buchanan, George Mifflin Dallas, Silas Wright, Jr., Nathaniel Pitcher Tallmadge, John Jordan Crittenden, Thomas Hart Benton, William Rufus de Vane King of Alabama, John Forsyth, William Cabell Rives, John Tyler, Benjamin Watkins Leigh, Littleton Waller Tazewell, John Middleton Clayton, Felix Grundy, Alexander Porter, Willie Person Mangum, George Poindexter, Samuel Lewis Southard, Theodore Frelinghuysen, and Josiah Stoddard Johnston. He soon became one of the leaders of the opposition to President Andrew Jackson's administration. His keen intellect, demonstrated time and again in the speeches he delivered on the Senate floor, earned for him the title "Logician of the West." During his term in office he supported Clay's "American System" which called for protective tariffs and internal improvements, he advocated the re-charter of the United States Bank, he denounced Jackson's removal of deposits from that Bank as well as his "Specie Circular," he advocated reduced postal rates, and he brought about a revision of the land laws, a reorganization of the Post Office Department, and a bill for the settlement of the Ohio-Michigan boundary dispute. Despite his opposition to the Jackson Administration he supported the Force Bill as a remedy for nullification.
Within six weeks of entering the Senate he was elected a member of the important special committee set up to deal with the application of the Bank of the United States for a new charter. When the Ohio legislature "instructed" him to use his influence to prevent the rechartering of the Bank, he disputed their authority to so control his conduct as a Senator, insisting that Senators represented their State, the sovereign power, rather than the Legislature. As a member of the Committee on Post-Offices and Post-Roads which had been investigating irregularities in the Post Office Department, on June 9, 1834, he delivered to the Senate the majority report which vigorously assailed the abuses and corruption in that Department. In return, he was violently assailed by the administration press, which found a ground of attack conveniently at hand. As a member of a Committee on Revolutionary Claims, Ewing had favored the issuing of land warrants to claimants. However, before entering the Senate he had speculated in Virginia landscrip and thus stood to profit personally from his actions as a Senator. His opponents quickly took up the charge and, indeed, he was not free of such attacks until after the Civil War when he was past seventy.
His opposition to the Jackson Administration and his refusal to follow the "instructions" of the Ohio Legislators had helped to undermine his position back home in Ohio where a pro-Administration party had come to power within the Legislature. Consequently, in January 1836, he was defeated in a bid for re-election as a result of prior redistricting which gave