Campaign finance reports filed Monday show Richards raised $37,000 in July and spent $39,700. He faces Susan Happ and Ismael Ozanne in an Aug. 12 Democratic primary.
Happ finished the month with $131,000 in the bank. She collected $43,000 in July and spent $32,000.
Ozanne had a cash balance of $7,700 on July 28. He brought in $15,500 and spent $11,000.
The primary winner will face Brad Schimel, the only Republican in the race. He had $418,000 in the bank at the end of July after raising $54,000 and spending $36,000.