Did we keep a republic?

On September 17, 1787, the final day of the Constitutional Convention in Philadelphia, Benjamin Franklin, 81, shared with his fellow delegates his assessment of the new Constitution:

I confess that there are several parts of this Constitution which I do not at present approve, but I am not sure I shall never approve them: For having lived long, I have experienced many instances of being obliged by better information, or fuller consideration, to change opinions even on important subjects, which I once thought right, but found to be otherwise.