Iowa likely voters closely split on income tax constitutional amendment, poll finds

Likely Iowa voters do not have a clear preference on a proposed constitutional amendment requiring two-thirds of state lawmakers to approve income tax increases, according to a new Suffolk University poll.

The Suffolk University Political Research Center poll, released Wednesday, found roughly 33% of likely Iowa voters planned to vote “yes” on Amendment 1, while 36% planned to vote against the amendment. An additional 30% said they were still undecided, while 1% refused to answer the question.

The poll, conducted by the Suffolk University Political Research Center, largely focused on the Iowa gubernatorial and U.S. Senate races. But the poll also asked likely voters about other subjects, including their top priorities for Iowa’s K-12 education system and agricultural economy and the constitutional amendment.

The proposed amendment to the Iowa State Constitution would require any future increases to the state’s personal income or corporate tax rates to gain supermajority approval at the Iowa Legislature in order to pass. The language specifies this requirement would not apply taxes imposed by local governments.

In Iowa, amending the state constitution is a multi-year process. Lawmakers had to pass Senate Joint Resolution 11 through two consecutive sessions for it to appear on the Nov. 3, 2026 ballot. A simple majority of voters must approve the language included in the ballot question to amend the state constitution.

The poll of 500 likely midterm voters was conducted between Aug. 20 and 23 and has a margin of error of plus or minus 4.4 percentage points. This means the three-point difference between approval and disapproval falls within the statistical margin of error.

The results also show there are a significant number of Iowans who still have to make up their minds on the ballot question. Organizations like Iowans for Tax Relief, an advocacy group that supports lower taxes and “less government,” launched an awareness campaign about the constitutional amendment in July.

When lawmakers discussed the proposed constitutional amendment, Republicans who supported the measure said requiring two-thirds of lawmakers approve raising income tax protects taxpayers. But Democrats argued the requirement would restrict future state lawmakers from being able to address a state budget crisis amid declining revenues.

Though Republican and Democratic lawmakers largely voted along party lines on whether to place the constitutional amendment on the ballot, Iowa voters’ opinions on the proposal were not as closely tied to their party affiliation.
According to the poll, 39% of Republicans said they would vote to support the constitutional amendment, but 33% said they planned to vote against the measure and 28% remain undecided.

There was more opposition to the proposal among Democrats and independents, but the margins were still relatively close. The poll found 35% of Democrats opposed the constitutional amendment, while 27% supported it and 37% were undecided. For independents, 41% opposed the proposal, 31% supported it, and 27% were undecided.

In addition to the question on the constitutional amendment, the Suffolk University Poll also found Republican U.S. Rep. Ashley Hinson leading in the U.S. Senate race against Democratic state Rep. Josh Turek 45% to 41%, and Democratic State Auditor Rob Sand leading against Republican businessman Zach Lahn 48% to 44%. These results were also within the poll’s margin of error.