Unfortunately, Florida is an at-will state. Your employer can demote or fire you for any reason or no reason at all. However, if you were chosen for demotion when others weren't, then you might look to see if the demotion was for an illegal reason. For instance, were others of a different race, age, sex, religion, national origin, marital status, or color chosen to keep their positions when you were demoted? Or had you recently revealed a pregnancy or disability? Had you recently taken FMLA leave or made a worker's comp claim? Had you recently objected to or refused to participate in illegal activity? Had you recently reported sexual harassment or discrimination? If any of these situations had occured, then we'd look to see whether the individuals kept in their positions were less qualified or had less seniority than you; what reason the employer gave (if they won't give a reason, then they'll have a hard time later claiming they had a legitimate reason); and whether there was some disciplinary history.
If you think you were demoted because of some protected status or activity, then contact an attorney who handles employment law to see if you have potential claims against the employer.