If the candidate they support loses, nearly four in 10 said they would have little or no confidence that the election had been conducted in a fair-and-square way, setting up what could be a debate over the legitimacy of the next president. Those expressing doubts crossed partisan lines – 30% of Republicans and 45% of Democrats – although they identified different threats to the electoral process.

In the crowded Democratic contest, former Vice President Joe Biden retained a wide lead, at 32%, up 2 percentage points from the USA TODAY/Suffolk poll taken in June. But Massachusetts Sen. Elizabeth Warren moved up 4 points to second place, at 14%, and Vermont Sen. Bernie Sanders dropped 3 points, now at third place with 12%.

The sense of towering stakes has been stoked by President Donald Trump, whose sweeping policies and provocative rhetoric has convinced some that he is protecting basic American precepts and others that he is undermining them. If the election were held today, 41% said they would vote for an unnamed Democratic nominee, 39% for Trump. Ten percent said they would vote for a third-party candidate and another 10 percent were undecided.