The great debate between Abraham Lincoln and Stephen A. Douglas came on in Illinois (per this passage), and Douglas was chosen senator again.

The evidence

• “The great debate between Abraham Lincoln and Stephen A. Douglas came on in Illinois in 1859 and the county fairly shook from one end to the other. Douglass won, and was chosen again senator from the State of Illinois.”

  1900-caswell-reminiscences/10-politics-and-congress.md, PDF pp. 3–27

  Caswell, Lucien Bonaparte. The Reminiscences of the Hon. L. B. Caswell. Written at Fort Atkinson, Wis., 1914–1916; four-column newspaper reprint, newspaper and date unidentified. University of Wisconsin-Madison Libraries.

  Grade A: Found on a page of one of our sources