JEFFERSON CITY -- A coalition of Kansas City civic groups and statewide unions have a message for Gov. Jay Nixon.

Take a stand.

The groups have sent a letter to Nixon asking him to oppose Proposition A. Nixon, as he has on a variety of controversial issues lately, has refused to take a position.

"Our organizations strongly oppose Proposition A," the letter reads. "We were very disappointed to learn that you have not taken a firm position against Proposition A, and we encourage you to take a strong, public position against this ballot measure."

The letter was signed by representatives of the Greater Kansas City Chamber of Commerce and Mark Jorgenson, president and CEO of US Bank, as well as the leaders of several statewide unions, such as the Missouri National Education Association, SEIU and AFL-CIO.

Proposition A was put on the ballot by a group called Let Voters Decide. If voters pass it, then earnings taxes like the 1 percent taxes in St. Louis and Kansas City would be banned, and the two big Missouri cities would have to vote on whether to keep their earnings taxes next April.

The effort is funded by retired St. Louis businessman and philanthropist Rex Sinquefield, who has become Missouri's most prolific political donor in the past few years. Sinquefield, a critic of the earnings tax, has spent more than $6 million on Proposition A.

Since Proposition A made the ballot, leaders in Kansas City and St. Louis have taken different approaches to it. St. Louis Mayor Francis Slay, who counts Sinquefield as a major campaign donor, has said he will fight to keep the earnings tax in April, but will not expend much energy fighting the statewide ballot issue. Leaders in Kansas City have been more aggressive in speaking out against Proposition A.