Horner's administration was marked by integrity and a strong commitment to both conservative fiscal management and the needs of the indigent and those in state institutions.

[citation needed] His insistence on stopping graft and keeping state payrolls free of non-working patronage appointees put him at odds with the Democratic political organization of Chicago run by Patrick Nash and Mayor Edward Joseph Kelly.

[citation needed] They backed a rival candidate in the 1936 primary,Herman Bundesen, the President of the Chicago Board of Public Health and a well-known physician,[3] who carried Cook County, but whom Horner defeated with the help of a large downstate vote.

He supported the election of Scott W. Lucas to the Senate in 1938 to succeed retiring incumbent William H. Dieterich, who had proven to be anti-Semitic and somewhat pro-German.

[citation needed] Horner suffered a stroke four days before the November election and spent five months recovering in Florida before returning to Illinois, too late to mount the campaign he had wanted to lead against the re-election of Mayor Kelly.

The Horner Collection is now stored and partly displayed in the Abraham Lincoln Presidential Library and Museum in Springfield, Illinois.