Tax-limiting Proposal 5 should be defeated at the polls because two things are certain if it passes.

A billionaire’s family will have orchestrated a government-crippling change to Michigan’s constitution, and the state’s residents will suffer the consequences.

The proposal — to require a two-thirds “super majority” of lawmakers to pass a tax increase, or statewide voter approval — would not ensure strong consensus, as backers argue.

This is minority rule, where as few as 13 senators could trump 135 other lawmakers.

Gridlock will result. The Legislature that led to 2007’s near budgetary meltdown would look functional by comparison.

Tax-reform efforts that were central to Gov. Rick Snyder’s first year could not have happened. Businesses would still have the hated Michigan Business Tax because offsetting increases would not have been possible.

Indeed, no one on either side can recall a tax that passed by two-thirds of each chamber. It does not happen, but this would: The state’s bond rating will suffer as lenders became wary of our ability to maintain revenue.

There also would be inevitable fee increases as state officials look for revenue alternatives they can control. Want to pay untold more for a license plate? How about public university tuition hikes that make earlier increases seem tame? Local officials may be forced to seek higher property taxes, or impose deep cuts, to offset dwindling state revenue.

One need only look to California, considered by many to epitomize budgetary dysfunction, for a vision of the future.

Arguably, this proposal - more than others on the ballot - does fit within a constitutional framework, but the process by which it got on the ballot is a perversion of democracy.

The effort, including paid petition gatherers, is largely bankrolled by the family of Ambassador Bridge owner Manuel “Matty” Moroun. The Morouns are also bankrolling efforts to block a competing publicly owned bridge between Windsor and Detroit.

Nearly $3.5 million has been donated to the “two-thirds” proposal by the Moroun-affiliated Liberty Bell Agency Inc., campaign finance documents filed last week show.

Why? One possible reason is to protect tax policies that benefit the family’s business interests, forget the impact on others. Those favorable policies would require a near-impossible super majority to revoke.

The Morouns aside, known groups that support Proposal 5 are relatively few. Many originate elsewhere: Americans for Prosperity, Americans for Tax Reform, Michigan’s chapter of the National Federation of Independent Business. It is disappointing Attorney General Bill Schuette is among supporters.

By contrast, a wide range of groups that normally disagree - from unions such as the United Auto Workers to business groups such as the Michigan Chamber of Commerce - agree on Proposal 5, as do we.

It must be defeated.

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