From a speech by William A. Allen:

The relation between the Declaration and the Constitution has a different affect today than it did in 1860, when enemies to the more perfect union could find no pillar bearing more weight—and thus to be dislodged—that what they called the “self—evident lie” that “all men are created equal.” Those critics insisted that men indeed are not by nature made equal, nor should be. Today’s enemies of the more perfect union believe that “all men” in 1776 only meant all white males and, moreover, that not even they were by nature made equal though they should be. These critics insist, however, that what nature and history refused to humankind law can create (and they would indeed have all men equalized, the Constitution notwithstanding).

In 1860 nothing and no one so stoutly resisted the enemies of the Declaration than the Defender of the Constitution. Today nothing and no one so stoutly resists the enemies of the Constitution than the Defender of the Declaration. Abraham Lincoln established at Gettysburg that the nation “conceived in liberty” and confirmed “in the proposition that all men are created equal” must conduct its affairs through limited, constitutional union. Today we require to learn that limited, constitutional union can only be justified on the basis of the Declaration of Independence. What we mean, then, when we say that the Declaration of Independence and the Constitution are best friends, is that they are necessary and reciprocal supports for each other.