Why do incumbent politicians try to typecast “qualified candidates”?

Having developed his talents, tried his virtues, and developed practical insight into his own wants and duties, William Barlow, III, has surpassed all requirements that ensure experience, knowledge and maturity prescribed by Article I, section 3 of the United States Constitution. William’s interests are properly aligned with the inhabitance of the State of Oregon and his qualifications consistent with the standards necessary to be elected to the U.S. Senate. 

Although additional qualifications are occasionally suggested, the 1969 Supreme Court decision in the case of Powell v. McCormack conclusively established that the constitutional qualifications for Members of Congress under Article I are exclusive.

It is William’s belief that the suggestion of additional requirements is most commonly an effort to typecast a “qualified candidate” in the image of an incumbent legislator who seeks to fortify their position and bias the electorate against competent opponents while preserving the institutional status quo.  Alexander Hamilton observed, ‘‘[t]he qualifications of the persons who . . . may . . . be chosen . . . are defined and fixed in the Constitution, and are unalterable by the legislature.”