A turbulent month in politics contributed to a decline in millionaire investors’ confidence in August, according to Spectrem Group’s Millionaire Investor Confidence Index released Tuesday.

The political upheaval is creating uncertainty about the direction of the American economy, Spectrem says. The index dropped from a 12 in July, which Spectrem considers mildly bullish territory, to a 10, which is neutral.

The decline for millionaires contrasted to a one-point increase in Spectrem’s Affluent Investor Confidence Index from 6 in July to 7 in August, which leaves it in neutral territory.

The decline in millionaire sentiment is the first since May. The millionaire index measures confidence of investors with $1 million or more in investable assets and the affluent index includes investors with $500,000 to $1 million in investable assets.

Historically, the Spectrem indices show greater investment optimism among millionaires than non-millionaires, but for August they were reversed. Only 43.9 percent of non-millionaires said they would avoid investing in the coming month, a drop from 52.3 percent in July.

Asked to name the story most affecting their economic outlook, 40 percent of investors named the political environment as the prime factor.

“Volatility is generally low in August, as it is a slow month economically, and Congress is on its summer recess,” says Spectrem President George H. Walper Jr. “However, this year we experienced rising tensions with North Korea, fallout from Charlottesville and ongoing tensions between the President and Congress about health care, tax reform and the border wall with Mexico. It is a time of social and political uncertainty, and the indices reflect that.”