(Editor's note: The version of this editorial that originally was posted on Sept. 7 contained incorrect figures for the amounts of money that Rex Sinquefield has contributed to the "Let Voters Decide" campaign and the amount that was spent on gathering signatures. This version has been updated with correct information.)

On Nov. 2, Missouri voters will be asked whether they want to make major changes to state tax law.

If Proposition A wins statewide, voters in St. Louis and Kansas City would be required to hold an election every five years on whether to continue their city earnings tax. If Proposition A passes, the first such election would be in April 2011. Unless voters opted to continue the city earnings tax, it would be phased out over 10 years and could not be reimposed.

Proposition A passage also would bar other municipalities without a current city earnings taxes from enacting one.

The initiative made the statewide ballot because Rex Sinquefield, a retired investment adviser and free-market activist, spent has contributed $6.8 million to the campaign, of which about $760,000 has been spent on the firm hired to circulate petitions and gather signatures throughout Missouri.

His campaign secured signatures from 160,393 registered voters, far exceeding the necessary 114,680 to make the ballot. Mr. Sinquefield paid an average of about $4.70 per signature to the signature gathering firm.

By the time the signatures had been filed with the Missouri Secretary of State on May 2, another $316,548 had been spent on campaign management, $65,530 on legal services, $33,705 on internet outreach, and $25,115 on media support, according to filings with the Missouri Ethics Commission. A July filing reveals that another $4.08 million has been spent on media purchases.

But for all the money Mr. Sinquefield invested to propel Proposition A, astonishingly little effort has been made to inform voters of everything that is at stake.

The campaign supporting Proposition A carries a disarmingly simple slogan: Let voters decide.

But what, exactly, are voters being asked to decide?

Mr. Sinquefield casts the initiative as a referendum on income taxes. He has said that he thinks that such taxes are counterproductive and have contributed to economic stasis in St. Louis and Kansas City. That’s an interesting theory, but one about which there is considerable disagreement among economists.

And Proposition A forces voters to decide much more than whether they like earnings taxes.

Voters also would have to decide how to pay for local services if the earnings tax is abolished. Earnings tax revenue, after all, accounts for at least 30 percent of St. Louis’ and Kansas City’s operating budgets, helping to pay for police and fire protection and other basic services.

“No one is talking about getting rid of the revenue,” Mr. Sinquefield told us in February. “It has to be replaced.”

But how?

We posed that question to Mr. Sinquefield in February. He offered no specifics — and none appear on the campaign website.

“That was the reason that we proposed a 10-year phase-out,” he told us, “so you have a lot of time to figure this out.”

Actually, if Prop A passes and local voters opt to discontinue the tax, St. Louis and Kansas City immediately would be forced into emergency mode. Ten percent annual cuts would begin in 2012 and continue each year for 10 years.

On Tuesday, we again posed the “but how” question to Mr. Sinquefield. We got back an e-mailed response from Laura Slay, whose public relations company represents Mr. Sinquefield: “Rex does not have a proposal,” Ms. Slay said. She referred other questions to the Let Voters Decide campaign office.

The loss of e-tax revenue would reverberate beyond the residents of St. Louis and Kansas City. Voters throughout both metropolitan regions would face increased uncertainty as their core cities struggled to find replacement revenue. As go the metro areas, so goes Missouri.

Voters outside of the two big cities must decide whether to cede local control over their home communities. And there’s a larger question: Is a multimillion-dollar campaign funded by a wealthy individual — based on economic theory that is questionable at best — good for democracy?