Funny, I thought Lyndon Johnson said that. Maybe he was just quoting it.
Per Reuters Fact Check team:
> Misattributed. There is no evidence Lincoln ever made such a statement about testing a man’s character. The author appears to be Robert G. Ingersoll, who used this phrase to describe the 16th president of the United States on several occasions in the 1890s [1].
[1] https://www.reuters.com/article/factcheck-abrahamlincoln-pow...