The Hatch Act applies to federal employees, employees of the District of Columbia and certain employees of state and local governments.  According to 5 USCS § 7322 (1) “employee” means any individual, other than the President and the Vice President, employed or holding office in–
      (A) an Executive agency other than the General Accounting Office [Government Accountability Office];
      (B) a position within the competitive service which is not in an Executive agency; or
      (C) the government of the District of Columbia, other than the Mayor or a member of the City Council or the Recorder of Deeds;
   but does not include a member of the uniformed services.

The Hatch Act applies to an individual employed by a state agency whose principal employment is in connection with an activity which is financed in whole or in part by the federal government.  The federal government has a legitimate interest in making sure that state programs funded in whole or in part with federal dollars be administered in a non-partisan manner, and in ensuring that the public not perceive that those employees involved in administering the programs are partisan politicians exerting inappropriate partisan influence.  The Act’s prohibition on candidacy for elective office is rationally related to the government’s interest because it allows the government to remove actual or apparent partisan influence from the administration of federal funds.  

In United Public Workers v. Mitchell, 330 U.S. 75 (U.S. 1947) the United States Supreme Court cited three primary Congressional interests underpinning the Hatch Act, : (1) the elimination of political factors as a possible basis for preferential treatment of employees by their supervisors; (2) the prevention of political leaders using government employees to build “political machines”; and (3) prevention of the cumulative effect on morale of political activity by all employees who could be induced to participate actively. 

According to 5 C.F.R. § 734.601, the Hatch Act also applies to an employee who works on an irregular or occasional basis or is a special Government employee when he or she is on duty.  The regulations provide, as an example, that an employee appointed to a special commission or task force who does not have a regular tour of duty may run as a partisan political candidate, but may actively campaign only when he or she is not on duty.