Referendum 1|
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| Choice | Votes | % |  
| Yes | 1,264,310 | 59.43% |  
| No | 862,924 | 40.57% |  
| Valid votes | 2,127,234 | 97.44% |  
| Invalid or blank votes | 55,921 | 2.56% |  
| Total votes | 2,183,155 | 100.00% |  
| Registered voters/turnout | 4,256,721 | 49.97% |  | 
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| Yes   90–100%    80–90%    70–80%    60–70%    50–60%  | No   90–100%    80–90%    70–80%    60–70%    50–60%  | Other   Tie    No data    |  | 
| Sources: | 
Wisconsin Referendum 1 of 2006 was a referendum on an amendment to the Wisconsin Constitution that would invalidate same-sex marriages or any substantially similar legal status. The referendum was approved by 59% of voters during the general elections in November 2006. All counties in the state voted for the amendment except Dane County (home of the state capital, Madison, and the University of Wisconsin), which opposed it. The constitutional amendment created by Referendum 1 has been effectively nullified since June 26, 2015, when the United States Supreme Court ruled in Obergefell v. Hodges that state-level bans on same-sex marriage are unconstitutional.