5 U.S.C. § 1502: Influencing elections; taking part in political campaigns; prohibitions; exceptions

(a) A State or local officer or employee may not—(1) use his official authority or influence for the purpose of interfering with or affecting the result of an election or a nomination for office; (2) directly or indirectly coerce, attempt to coerce, command, or advise a State or local officer or employee to pay, lend, or contribute anything of value to a party, committee, organization, agency, or person for political purposes; or (3) if the salary of the employee is paid completely, directly or indirectly, by loans or grants made by the United States or a Federal agency, be a candidate for elective office. (b) A State or local officer or employee retains the right to vote as he chooses and to express his opinions on political subjects and candidates. (c) Subsection (a)(3) of this section does not apply to—(1) the Governor or Lieutenant Governor of a State or an individual authorized by law to act as Governor; (2) the mayor of a city; (3) a duly elected head of an executive department of a State, municipality, or the District of Columbia who is not classified under a State, municipal, or the District of Columbia merit or civil-service system; or (4) an individual holding elective office.