that's normal 18
Declaration of Independence mostly reflected the vision of liberal Americans, such as Thomas Jefferson.
There are two camps among founding fathers: pro-Republic-elite rule system (such as Franklin, Adams, Hamilton) vs. pro-平民统治 system (such as Thomas Jefferson). The latter was the minority 200 years ago.
George Washington was a smart fence sitter: he watched both sides fighting against each other and stayed as a well-respected impartial balancer in the system. He SELDOM expressed his own political vision.
Constitution is the compromise among all kinds of interests groups (such as the slave-owners in Southern States). Therefore, these two documents are not consistent in philosophy. Not surprising.
兄弟是高才，隔着个大洋就能看透这些文件之间的冲突。本人是在美国图书馆的political science 专著上看到历史学者的说明才醒悟的。
deeply in its national soul, there are two different conflicting visions originating from their founding fathers.
The current U.S. history books (high schools, primary schools) gave kids the impression that founding fathers are 铁板一块，bunch of harmonious patriots who fought for welfare/interests of average Americans UNSELFISHLY. The fact is that they were just bunch of large slave owners and landowners who refused to pay taxes to Westminister without their rep. there. They just wanted to be their own masters and control their own fate and wealth.
At the same time, this bunch of people are DEEPLY DIVIDED, and VERY different from each other. They fought with words, persuasion and debates. They changed alliance over time. But 不同于中国的政治精英--动不动就用战争来解决彼此间的差异，分歧，美国的founding fathers 更善于妥协，用各种政治设计-妥协方案-时间的积累来减轻矛盾。
In sum， 斗而不破。