As a general rule, the First Amendment to the U.S. Constitution makes it unlawful to discharge or demote an employee because the employee supports a particular political candidate. This is not an absolute rule; there are exceptions that can come into play, usually depending on the nature of the employee's job.
But the protection is important: the Supreme Court ruled recently in Heffernan v. City of Paterson that the protection applies even where the employer is mistaken about the employee's political activity if the reason for the demotion or discharge is a desire to prevent or punish the employee for his or her political activity.
These are usually referred to as political discrimination cases.
Lexington, Kentucky employment lawyer Robert Abell represents individuals and employees in political discrimination cases; contact him at 859-254-7076.