Wis. Stat. § 180.1131: Shareholder vote.

In addition to a vote otherwise required by law or the articles of incorporation of the resident domestic corporation, a business combination must be approved by the affirmative vote of at least all of the following, except as provided in s. 180.1132:

(1) Eighty percent of the votes entitled to be cast by outstanding voting shares of the corporation, voting together as a single voting group.

(2) Two-thirds of the votes entitled to be cast by holders of voting shares other than voting shares beneficially owned by a significant shareholder who is a party to the business combination or an affiliate or associate of a significant shareholder who is a party to the business combination, voting together as a single voting group.