As the markets soar into blue skies, investor confidence among the jet set took a nosedive last month.

This fall was all the more dramatic since the outlook of the well-heeled was sitting on a four-year high as recently as April, according to the Millionaire Confidence Index from research and consulting firm Spectrem Group. Then it took the biggest one-month fall in the 13 years that Spectrem has published the survey. In fact, it’s the first time in the past six years that millionaires’ confidence fell below that of the affluent segment, defined as households with at least $500,000 in investable assets. The affluents’ confidence fell in May too, but not as far or from the same heights that millionaires had enjoyed in April.

This index ranges from -50 (the most bearish) to 50 (the most bullish). Millionaires fell to a level of 3 in May from 20 in April. Affluent investors declined to 6 from 10. For perspective, at a level of 20, millionaires were “mildly bullish,” as Spectrem defines its index, in April. At a level of 3, they were squarely in neutral category in May.

“Although non-millionaires also recorded a drop in confidence, the fact they are slightly more confident now than millionaires is a strong indication that we may be entering a tumultuous period for investors,” Spectrem President George Walper Jr. said in a press release.

The irony in this loss in confidence is that it happened against a backdrop of a bull run in the U.S. market. Indeed, the S&P 500, as measured by both Vanguard’s and State Street’s ETFs, returned 1.4% in May alone, capping a six-month run of 10.7% annualized.

So what caused the record-breaking drop? Spectrem pointed to turbulence in Washington and “significant doubt” about the tax reform promised by President Trump, as well as concerns over the recently submitted proposed federal budget. Indeed, more than half of investors surveyed (54%) cited the political environment as the story in the news most affecting their economic outlook, dramatically greater than any other topic.

Conventional wisdom would suggest the attitudes and sentiments of the general population will follow the millionaires, said Tom Wynn, director at Spectrem. But he also noted that “normal conventional wisdom isn’t so normal anymore.” Instead of one investor segment following another, he said that a better sense of direction from Washington is what’s most needed.

"I believe we will continue to see some ups and downs in both the millionaire index and the affluent index until we get a better direction of what the current administration is going to do.”

Indeed, investors will continue to be cautious until “we get some clear direction in what President Trump will do and a barometer of how the business community will react to his plans.”