Question

A potential juror who worked with a litigant may likely be disqualified as a juror based on a challenge for cause

Answer 1

That statement is true.

A challenge of cause could be applicated if any parties have an acceptable basis to assume that the juror wouldn't be able to fairly judge based on the evidence.

Having the experience to work with the litigant may cause the potential juror to form a close personal relationship and most likely become bias.