Over the issue of whether slavery should be allowed in all new western territories, Abraham Lincoln and Stephen A. Douglas disagreed during their debates. Hence, Option D is correct.
The debate was held from August 21, 1858, till October 15, 1858, in Illinois, United States. Basically, it was an event named "Freeport Doctrine." This was a series of seven debates.
The participants of the debate were Democratic senator Stephen A. Douglas and Republican challenger Abraham Lincoln. The major concerning issue was the extension of slavery into the territories.
Therefore, Option D is correct.
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