Lawyer, legislator, politician, state circuit judge Upon his graduation from Yale in 1835, Davis moved to
Bloomington, Illinois, to practice law. Davis served as a member of the
Illinois House of Representatives in 1845 and a delegate to the
Illinois constitutional convention in
McLean County, 1847. From 1848 to 1862, Davis presided over the court of the Illinois Eighth
Circuit, the same circuit where his friend, attorney
Abraham Lincoln, was practicing. Davis was a delegate to the
1860 Republican National Convention in Chicago, serving as Lincoln's
campaign manager during the
1860 presidential election and, along with
Ward Hill Lamon and
Leonard Swett, engineering Lincoln's nomination at the Convention. After President Lincoln's assassination, Judge Davis was an administrator of his estate. to succeed
John Archibald Campbell, a Southerner, who had resigned on April 30, 1861, after the outbreak of the
Civil War. Formally
nominated on December 1, 1862, Davis was confirmed by the
United States Senate on December 8, 1862, On the Court, Davis became famous for writing one of the most profound decisions in Supreme Court history,
Ex parte Milligan (1866). In that decision, the court set aside the death sentence imposed during the Civil War by a military commission upon a civilian,
Lambdin P. Milligan. Milligan had been found guilty of inciting
insurrection. The Supreme Court held that since the civil courts were operative, the trial of a civilian by a military tribunal was unconstitutional. The opinion denounced arbitrary military power, effectively becoming one of the bulwarks of held notions of American civil liberty. In
Hepburn v. Griswold (1870), he dissented from the Supreme Court's decision that Congress lacked the power under the Constitution to make paper currency
legal tender for debts contracted before the Legal Tender Act of 1862. After refusing calls to become
Chief Justice, Davis, a registered independent, was nominated for president by the Labor Reform Convention in February 1872 on a platform that declared, among other things, in favor of a national currency "based on the faith and resources of the nation", and interchangeable with 3.65% bonds of the government, and demanded the establishment of an eight-hour law throughout the country, and the payment of the national debt "without mortgaging the property of the people to enrich capitalists." In answer to the letter informing him of the nomination, Judge Davis said: "Be pleased to thank the convention for the unexpected honor which they have conferred upon me. The chief magistracy of the republic should neither be sought nor declined by any American citizen." Just as the Electoral Commission Bill was passing Congress, the
legislature of Illinois elected Davis to the Senate. Democrats in the Illinois Legislature believed that they had purchased Davis's support by voting for him. However, they had made a miscalculation; instead of staying on the Supreme Court so that he could serve on the Commission, he promptly resigned as a Justice, in order to take his Senate seat. Because of this, Davis was unable to assume the spot, always intended for him, as one of the Supreme Court's members of the Commission. His replacement on the Commission was Republican
Joseph Philo Bradley, resulting in an 8–7 majority for that party – which in turn awarded each of the 20 disputed electoral votes, and the Presidency, to Hayes by that outcome, 185 electoral votes to 184.
United States Senate Davis served only a single term as
U.S. Senator from Illinois (1877–1883), yet still played a meaningful role in U.S. history. Upon the assassination of President
James A. Garfield in 1881, Vice President
Chester Arthur succeeded to the office of president. Per the terms of the
Presidential Succession Act of 1792, which was still in effect, any subsequent vacancy of the office during the remaining 3½ years in Garfield's term would be filled by the
President pro tempore of the Senate. As the Senate was evenly divided between the parties, this posed the risk of deadlock. To prevent this the independent Senator Davis was elected to preside over the Senate. At the end of his term Davis did not seek re-election, instead retiring to his home in Bloomington. ==Personal life==