A declarative sentence is a statement that ends with a period. It states facts or an opinion and lets the reader know something specific. All of these sentences were declarative.
My reaction to this quote is that Abraham Lincoln is referring to the ideal that once people have power they tend to abuse it for their advantage, and personal gain. For Example, gerrymandering. Gerrymandering is the manipulation of the county sizing and grouping in states by the Legislative branch to guarantee their reelection into federal or state offices. A typically Democratic city perhaps may be grouped or redrawn to conjoin with a vastly Republican populated area, creating a larger group of supporters of one party, and a polarized county.
Noun or verb
is that what your asking?