So far, people, unions, and companies on both sides have raised more than $140 million for the six ballot initiatives.
Proposal 3 has become a spending war between utility companies and environmentalists, with some of the biggest spending out of the state.
"Proposal 3 has gotten tremendous support from outside Michigan, particularly from the San Francisco area, probably Silicon Valley," said Bill Ballenger of Inside Michigan Politics. "Now an ad has gone up with Bill Clinton supporting Proposal 3. The opposition to Proposal 3 has been very fierce from the business community."
That "business community" is mostly Consumers Energy and DTE Energy; each contributed more than $11.5 million against the constitutional amendment that would require the state to use 25 percent renewable energy by the year 2025. Those price tags are almost standard for the other proposals as well.
"Each side keeps upping the ante," Ballenger said. "You can make the argument they're canceling each other out, well yes, they are."
But he said no one is backing down yet. With millions already invested and only a week until election day, it's a crucial time when many voters make up their minds.
"A lot of the supporters and opponents of these proposals are going to be scratching their heads and thinking, 'You know, we spent $150 million on this, and maybe it doesn't really make any difference. We've got to spend $150 million more in the next week or it will all be wasted,' and they may do that. It could be $300 million," Ballenger said.
All of this could mean voters will focus more on who's funding the ads, rather than what the proposal is actually about.
"It should come down ultimately to what the proposal says, whether people think it would be a good thing for Michigan for this to be in our Constitution or a bad thing," Ballenger said. "But, other factors are going to creep into people's consciousness."
Right now Proposal 3 is in second place for the most expensive proposal campaign, but anyone could up the ante next. The last of campaign finance information isn't due until after election day.
This year's spending on ballot proposals is about 30 percent more than all of Michigan's state campaigns in 2010. The total two years ago was a little less than $108 million.