the spoil system
Andrew Jackson popularized and institutionalized the "spoils system" rewarding loyal party supporters with government jobs. "To the victor go the spoils."
Jackson believed this was a practice that would prevent corruption by constantly rotating positions with each new president. Problem was it often led to unqualified appointments. After the assassination of Garfield 1881 the landmark 1883 Pendleton Act created a merit system for federal jobs. It required most government positions be awarded based on competitive exams, not political favoritism. It also made it unlawful to fire, or solicit political contributions from employees.
It was signed into law by President Chester A. Arthur, and the Civil Service Commission was established. TR was appointed a commissioner in 1889 and served until 1895.
Initially it covered about 10% of the jobs, but gradually expanded, ushering in a more professional, less corrupt federal workforce.