AP Photo/The Detroit News, Steve Perez, File

In This Aug. 16, 2011 Detroit Federation of Teachers and two other unions demonstrate in Detroit to protest wage and benefit cuts imposed by an emergency manager authorized to void union contracts. Unions are supporting a 2012 statewide ballot initiative to put collective bargaining rights in the Michigan constitution. (AP Photo/The Detroit News, Steve Perez, File) (November 7, 2012)

DETROIT (AP) — Organized labor leaders in Michigan say they have no regrets about their unsuccessful push to add a guarantee of collective bargaining rights to the state constitution.

Union leaders and campaign strategists said Wednesday the ballot initiative known as Proposal 2 was rejected because its supporters were outspent by business-backed groups that ran ads sowing confusion about what the measure would do.

State AFL-CIO President Karla Swift says labor had no choice but to seek a constitutional amendment after the Republican-led Legislature and Gov. Rick Snyder chipped away at their ability to negotiate fair wages and working conditions.

Steve Cook of the Michigan Education Association says opponents won through misleading and scurrilous attacks on teachers, including the claim that the proposal would abolish laws requiring criminal background checks for teachers.