Does an employer have to give preference to a qualified applicant with a disability over other applicants?
No. According to the U.S. Equal Employment Opportunity Commission's website called The ADA (Americans with Disabilities Act): Questions and Answers, "An employer is free to select the most qualified applicant available and to make decisions based on reasons unrelated to the existence or consequence of a disability." A detailed job description can be used to compare job candidate skills and experiences as they relate to the open position.
For more information about the ADA, view the Knowledge Base article How can employers keep up with how the ADA and the ADAAA are being applied in the area of employment?