The belief crossed party lines, with roughly the same percentage of Republicans, Democrats and independents expressing that view, the New York Times/CBS News poll indicated.
Only 13 percent, or about 1 in 8, said the justices decide cases based solely on legal analysis. Four percent said it "depends" and 8 percent said they didn't know.
Overall, 44 percent of Americans approve of the job the court is doing, the poll found. Thirty-six percent disapprove and 20 percent don't know.
Liberals and conservatives both registered about 40 percent approval rates of the court.
Court approval was as high as 66 percent in the late 1980s and more recently was near 50 percent, the Times said.
By contrast, 15 percent of Americans said they approved of the job Congress is doing, while 77 percent said they disapproved.
The public expressed doubts about life tenure for Supreme Court justices, with 60 percent agreeing that "appointing Supreme Court justices for life is a bad thing because it gives them too much power." One-third agreed with a contrary statement, that life tenure for justices "is a good thing because it helps keep them independent from political pressures." Seven percent said they didn't know.
The poll found more than two-thirds of Americans hope the court will overturn some or all of the 2010 healthcare reform law when it rules on it, most likely this month.
Forty-one percent said they want the court to throw out the entire Patient Protection and Affordable Care Act, 27 percent want the court to overturn the so-called individual mandate generally requiring uninsured individuals to buy government-approved health insurance starting in 2014, and 24 percent want the court to keep the entire law, the poll found. Eight percent said they didn't know.
Forty-three percent of respondents saying they hope the court will strike down the healthcare law said they approved of the court's work, but so did 41 percent of those who favored keeping the law.
The phone poll of 976 adults conducted May 31 through June 3 had an average margin of error of 3 percentage points.