Hinds County Republican Party chairman Pete Perry says 300 to 350 possibly illegal votes were found in Mississippi's largest county in the Senate runoff between incumbent Thad Cochran and challenger Chris McDaniel.
The total is significantly lower than McDaniel's assertion that at least 1,500 improper votes were found in Hinds County.
McDaniel has said he would announce Wednesday whether he would formally challenge his loss to Cochran.
Mississippi voters don't register by party, but state law prohibits a person from voting in one party's primary and the other party's runoff in the same election cycle.
The two campaigns have been examining poll books and ballot boxes statewide to see if people marked as voting in both the June 3 Democratic primary and the June 24 Republican runoff.