The Clean Michigan Initiative was conceived during the administration of Gov. John Engler, and was approved by both the Legislature and voters as required by state law.
The Michigan Constitution requires the approval of two-thirds of the Legislature and a majority of voters before general obligation bonds may be issued. Lawmakers authorized the CMI ballot measure on July 27, 1998, and designated the bond proceeds for "environmental and natural resources protection programs that would clean up and redevelop contaminated sites, protect and improve water quality, prevent pollution, abate lead contamination, reclaim and revitalize community waterfronts, enhance recreational opportunities, and clean up contaminated sediments in lakes, rivers, and streams."
Appearing on the ballot as "Proposal C," the initiative passed on Nov. 3, 1998 with 63 percent of the vote (1,821,006 to 1,081,988). Support for the measure was most pronounced in the state's urban areas.
The measure faced little organized opposition, as is common for such seemingly well-intended proposals. And voters tend to relegate environmental protection to government in the absence of a familiar alternative.
One of the only public figures to express misgivings about the initiative was Geoffrey Fieger, the 1998 Democratic gubernatorial candidate, who complained that the measure would not toughen environmental enforcement.  Otherwise, endorsements poured in from public and private groups alike, including the Michigan Municipal League; the Urban Core Mayors; the Michigan Township Association; the Southeast Michigan Council of Governments; the Michigan United Conservation Clubs; the Michigan Chamber of Commerce; and the Michigan Association of Realtors. 
Gov. Engler actively promoted Proposal C, persuading the Big Three automakers as well as major banks to help underwrite $2 million in advertising.  He also appointed then-U.S. Sen. Spencer Abraham, R-Mich., to headline the CMI campaign (which garnered Abraham significant free media in advance of his 2000 re-election bid).