The fraudulent driver’s license used to rent the post office box was also found during the search.
Several states, including historically Republican Utah, vote entirely by mail, and officials there said absentee ballots have not caused more election fraud.
The matter of absentee ballots for people with disabilities has been a major point of political and legal contention over the last few months.
Mohamed, who is running against incumbent Mayor Kevin Falconer, is being held at the Denton County jail.
“The fact an actual candidate for public office would engage in these activities is appalling,” said Denton County Sheriff Tracy Murphree.