Trump, the combative real estate mogul, leads the 16 other Republican candidates with 28 per cent support among registered voters nationwide, up from 20 per cent in a similar July 30 survey by Quinnipiac University.
Today's lead marks the widest margin for any Republican so far in the election cycle, the survey said.
Retired neurosurgeon Ben Carson placed a distant second with 12 percent, followed by former Florida governor Jeb Bush, Senator Ted Cruz and Senator Marco Rubio, each with seven percent.
"Other GOP hopefuls seem to disappear. Trump proves you don't have to be loved to be the leader," said Quinnipiac poll assistant director Tim Malloy.
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Trump's abrasive style, including his caustic criticism of rivals, has led some observers to say he does not have the temperament to be president, but he has dominated the race essentially since he declared his candidacy in June.
On the Democratic side, Clinton's support has shrunk, to 45 per cent now compared with 55 per cent on July 30, while her main rival Senator Bernie Sanders is polling at his highest level, 22 per cent.
Biden beats Trump by eight points, Bush by six points, and Rubio by three points.
Clinton beats them too but by smaller numbers: four points, two points and one point respectively.
Despite Trump's Republican lead, he has the highest negative favorability numbers in the field, at 36 per cent to 54 per cent. Bush is underwater as well, at 32-41, while Clinton's negative 39-51 matches her worst favorability rating ever.
Trump and Clinton are also seen as the least honest and trustworthy of the field.
Trump also tops the "no way" list, with 26 percent of Republicans saying they definitely would not support him.