Concerns about the U.S. presidential election and higher fuel prices have eroded U.S. affluent investors’ economic outlook, according to a survey published Wednesday.

Chicago-based consulting firm Spectrem Group said its affluent investor index for August recorded its second straight month with a neutral reading — trending toward bearish sentiment — after remaining mildly bullish in the first half of the year.

The index, which measures the investment outlook of U.S. households with US$500,000 or more in investable assets, dropped to its lowest level since February.

“Affluent investors grew increasingly pessimistic in August, with their investment outlook declining close to bearish levels,” said George Walper Jr., president of Spectrem Group. “ Concerns about the future of the U.S. economy were a big factor in this erosion. Just three months from Election Day, investors cited the presidential race as their biggest cause for concern about the economy, followed closely by higher oil and gas prices and to a lesser extent the Iraq War. With political issues front and center, it’s not at all clear what if anything will reverse this negative trend in sentiment prior to Nov. 2.”

The Spectrem Millionaire Index, which measures affluent households with investable assets of US$1 million or more, also declined in August, but remained in mildly bullish territory, reflecting the more optimistic investment outlook this group has expressed throughout the year.

When asked an open-ended question about which news events were driving their economic outlook, nearly half of all respondents cited either the presidential election (26%) or higher oil and gas prices (20%). Next was the Iraq War (11%), higher interest rates (5%), jobs and job security (4%) and terrorism (1%). When asked the same question in May, the presidential election was only an issue for 13% of those who responded.

The index is based on 250, 10-minute telephone interviews each month, giving the data a margin of error of plus or minus 6.2 percentage points.