OCPF rules on political campaign donations are summarized in the following points (which also cover checks sent to the campaign).
Corporate checks are prohibited!
Small business checks are generally not allowed, unless the check is specifically an unincorporated sole proprietorship.
Money orders and bank checks totalling greater than 50$ per year are prohibited.
Donations by a voter and spouse should be mailed on separate checks, unless both names are printed on the check form and BOTH persons sign the check. You can include multiple checks in one mailing envelope, for easiest Election Law compliance.