No person may solicit a candidate, political committee, political party or other person for money in exchange for an endorsement or an article in the news media supporting or opposing a candidate, committee or party.  RCW 42.17A.4780

All monetary contributions from political committees, political parties and caucus political committees must be by written instrument (e.g., check, money order, cashiers check, credit card transaction, wire transfer). Those from individuals, associations, unions or businesses must be by written instrument if the contribution is more than $100.  RCW 42.17A.475