Amendment 10 cleared the legislature this spring in response to a 2013 state Supreme Court decision that handed the governor broad powers to control state spending approved by the legislature.
While budget withholdings often are made when state tax collections fall short, the Supreme Court effectively gave the governor power to wait until the last day of the budget year regardless of tax collections.
The court based its decision on a constitutional provision giving the governor power to control the rate of spending.
In September, the Missouri legislature overrode 47 vetoes only to have the governor block funding for all 47 measures two days later. The governor can do that because Missouri prohibits deficit spending without voter approval. To make sure that's enforced, state laws give the governor broad powers to block the release of money appropriated for state programs.
Rep. Chris Kelly, D-Columbia, said with the amendment's approval, balancing the budget would be harder to do.
"The way it changes for the people of Missouri is that it makes an unbalanced budget much, much more likely," Kelly said. "It changes it for the General Assembly because it gives the General Assembly the opportunity to override the governor's withholds. But, the governor's withholds mechanism is the way that we in Missouri ensure a balanced budget, we have done so for many years."
He said the "governor's withhold mechanism" is a tool that has "kept the Missouri budget balanced and it's foolish to risk that for short term partisan gain."
Rep. T.J. Berry, R-Clay County, said it's the governor's abuse of his power that is causing the need for an improved system of check and balances.
"Our current governor has taken the powers that he needs to have, as far as he needs to be able to control the budget, and he has taken those powers and used them strictly for a tool of political necessity and means," Berry said. "If he had been like our previous governors, who sometimes walked over the line also but were much closer to the line, and didn't use the withholds as a weapon, I don't think we would even be having this discussion. But, our current governor has used withholds not as a budget necessity but as a budget weapon."
He said Nixon has had more vetoes overridden within the last four years than any other Missouri governors in the past 180 years combined.
"The reason why this governor has been overridden so much is his unwillingness to lead," Berry said. "When you start the legislative process in January and start working on bills and the governor's office does not show up until two weeks before the end of session, after all the work is done then says, no I don't like this, an awful lot of effort has been wasted and it makes it much harder to back up and change something."
Berry said he would like to see the governor collaborate with lawmakers.
"If he would engage with us in January, sit down and actually talk about where we have things in common and where we can work together, this governor could achieve a tremendous amount."
Nixon's office has called Amendment 10 "another attempt by the legislature to grow government beyond its means."
Nixon's press secretary, Scott Holste, said in an email that it would be "fiscally irresponsible" to add this provision to the Missouri Constitution.
"This authority to control spending is vital to keeping the state's fiscal house in order and is routinely cited by the ratings agencies in reaffirming Missouri’s AAA credit rating," Holste said in the email. "The Governor has made clear that amending the constitution to weaken Missouri's strong safeguards against overspending by the legislature would be fiscally irresponsible."
If the amendment is approved, a two-thirds vote would be required in both the House and Senate to override a withholding.