In February 1840, Anderson was elected to the United States Senate by the Tennessee General Assembly to the vacancy caused by the resignation of Senator Hugh Lawson White. He was a member of the Whig party whose resignation was orchestrated by Governor James K. Polk so that a Democratic senator could be appointed.[8][9][10][11] Anderson served in that body from February 26, 1840, to March 3, 1841, when the term expired.[12][13] In May 1840, he was a delegate to the national Democratic Party convention in Baltimore, Maryland.[14][15] Anderson did not stand for reelection to the seat; it was to remain vacant for a period when a group of Tennessee Democratic legislators called the "Immortal Thirteen" refused to meet and give a quorum sufficient to allow the election of a successor, apparently preferring no representation to that by a member of the other party, the Whigs.
After leaving the Senate, Anderson remained active in politics. In September 1844, he published a series of letters on the admission of Texas as a new state, which were published as a book.[16][17] In July 1847, he announced his support for Zachary Taylor of Louisiana as a candidate for President of the United States.[18]
Anderson was a leader of an overland company of leaving from Independence, Missouri, and going to California in 1849.[19][20] He served in the California State Senate in 1852 as a Democrat.[21] In February 1852, his name was put forward for U.S. Senator, but he lost the Democratic Party nomination.[22] He then was appointed by Governor John Bigler as an associate justice of the California Supreme Court, serving from April 6, 1852, to January 2, 1853, before returning to Tennessee in 1853 or 1854.[23][24][25] While in the California Supreme Court, he co-authored a ruling supporting the Fugitive Slave Act, writing, "Slaves are not parties to the Constitution, and although ‘persons,’ they are property."[26]
In 1821, he married Maria Hamilton in Washington, D.C., who died in 1825 in Jonesboro, Tennessee.[24] On June 7, 1825, he remarried married to Eliza Rosa Deaderick, his cousin, and they had 11 children.[24] She died October 15, 1866, in Knoxville, Tennessee.[28]
^Historic American Buildings Survey. "Historical and Descriptive Data". Rural Mount, Hamblen County, TN. U.S. Dept. of the Interior. Retrieved August 10, 2017.
^Tennessee Blue Book. Tennessee Secretary of State. 1890. p. 25. Retrieved August 9, 2017. Year 1821
^Force, Peter (1822). A National Calendar ..., Volume 3. Davis and Force. p. 135. Retrieved August 9, 2017. State Governments, The Floridas, Officers Appointed by the President in the Floridas..., Alexander Anderson, of Tennessee, to be Attorney of the United States for West Florida, and for that part of East Florida which lies westward of the Cape, to reside in Pensacola.
^"The Report of the Commissioners of Indian Affairs". The New York Herald. Library of Congress Historic Newspapers. January 6, 1848. p. 6. Retrieved August 9, 2017. Under the circumstances stated in my report of last year, the contract for their removal made on the 5th September, 1844, with Alexander Anderson and others, and which expired by limitation on the 31st December 1846, was extended to the 1st day of June last; yet, at the end of the period of extension there were nearly as many remaining East as had gone West.
^"Tennessee". Lexington Union (Lexington, MS). Library of Congress Historical Newspapers. February 14, 1840. p. 2. Retrieved August 9, 2017. Mr. Anderson is a tried and true Democrat-so we go.
^"Tennessee Senator". The North-Carolinian. Library of Congress Historic Newspapers. February 22, 1840. p. 3. Retrieved August 9, 2017.
^"Tennessee Senator". The Ohio Democrat and Dover Advertiser. Library of Congress Historic Newspapers. February 21, 1840. Retrieved August 9, 2017. Judge White...He is one of the old school Republicans
^"Twenty-Sixth Congress". The North-Carolina Standard (Raleigh, NC). Library of Congress Historic Newspapers. March 4, 1840. p. 3. Retrieved August 9, 2017. On the 26th, Mr. Grundy presented the credentials of the Honorable Alexander Anderson
^"U.S. Senate". Salt River Journal (Bowling Green, MO). Library of Congress Historic Newspapers. May 30, 1840. p. 2. Retrieved August 9, 2017.
^"National Democratic Convention". The North-Carolina Standard (Raleigh, NC). Library of Congress Historic Newspapers. May 13, 1840. p. 3. Retrieved August 9, 2017.
^"National Democratic Convention". The North-Carolinian (Fayetteville, NC). Library of Congress Historic Newspapers. May 16, 1840. p. 1. Retrieved August 9, 2017.
^"Letter of Alexander Anderson". The Daily Madisonian (Washington, D.C.). Library of Congress Historic Newspapers. September 16, 1844. p. 3. Retrieved August 9, 2017.
^"Gen. Anderson's Letter". The Daily Madisonian (Washington, D.C.). Library of Congress Historic Newpspapers. September 20, 1844. p. 2. Retrieved August 9, 2017.
^"Taylor Meeting at Knoxville". Boon's Lick Times (Fayette, MO). Library of Congress Historic Newspapers. July 10, 1847. p. 1. Retrieved August 9, 2017. Gen. A came out boldly for old Rough and Ready.
^"Intelligence by the Mails". The New York Herald. Library of Congress Historic Newspapers. February 11, 1849. p. 3. Retrieved August 9, 2017.
^"For California". The Daily Crescent (New Orleans, LA). Library of Congress Historic Newspapers. February 22, 1849. p. 2. Retrieved August 9, 2017.
^"Democratic Meeting in Sonora". Sacramento Transcript. Vol. 3, no. 17. California Digital Newspaper Collection. April 18, 1851. p. 2. Retrieved August 9, 2017.
^"Court of Claims". Washington Sentinel. Library of Congress Historic Newspapers. July 19, 1855. p. 2. Retrieved August 9, 2017. The following gentlemen...have been sworn in as attorneys of this court, viz: Alexander Anderson