Americans' attitudes toward the economy took a sharp turn downward in the third quarter, according to the CNBC All-America Economic Survey, with just 23% believing the economy will improve in the next year, the lowest level of optimism in three years.

The good news: Views on the current state of the economy (compared with the outlook) slid only modestly, with 48% of the public rating the economy as excellent or good, down from 51% in May, and 49% rating the economy as fair or poor, up just a point.

But with only 23% expecting economy to improve and 32% believing it will get worse, the poll marks the first time in the Trump presidency that economic pessimism outstrips optimism.

"October 2018 was the apex of the Trump economy,'' said Micah Roberts, partner with Public Opinion Strategies and the Republican pollster for CNBC. "There might be a new apex, but so far, that has been the point at which everything was going the best. ... This could be the beginning of a new Trump economy."

The optimism gauge has been trending down over the year, but the 7-point decline in from the prior survey is the biggest quarterly drop since 2011. The surge in the economic outlook that accompanied the election of President Donald Trump, which grew and then sustained over a nearly two-year period, has now been completely erased.

Stocks declined for a third day on Thursday after a reading of the services economy came in much worse than expected.