CHICAGO • Democrat Hillary Clinton has opened up a double-digit lead nationally over Republican Donald Trump, whose negatives remain unusually high for a presidential candidate amid early indications that the Orlando terrorist attack has had little direct impact on the 2016 race.

A Bloomberg poll shows Mrs Clinton leading Mr Trump 49 per cent to 37 per cent among likely voters in November's election, with 55 per cent of those polled saying they could never vote for the real estate developer and TV personality.

Most national polls in late May and early June showed a closer race, but they were taken before criticism intensified over Mr Trump's charge that a United States judge overseeing fraud cases against Trump University is biased because of his Mexican heritage.

Fifty-five per cent of likely voters in the new poll said they were very bothered by those comments. "Clinton has a number of advantages in this poll, in addition to her lead," said pollster J. Ann Selzer, who oversaw the survey. "Her supporters are more enthusiastic than Trump's and more voters overall see her becoming a more appealing candidate."

One bit of positive news for Mr Trump in the results is that he narrowly edged out Mrs Clinton, by 45 per cent to 41 per cent, when those surveyed were asked which candidate they would have more confidence in if a similar attack to the one in Florida took place a year from now. The violence, the worst mass shooting in US history, left 49 victims dead. Fifty per cent of likely voters also viewed Mr Trump as stronger in combating terrorist threats at home and abroad.

The Bloomberg poll is the first major telephone survey since the mass shooting, heightened furore over Mr Trump's statements about the judge, and Mrs Clinton's June primary victories in California and other states that cemented her status as the presumptive Democratic nominee. The poll was conducted from Friday to Monday, with additional questions about terrorism, guns, and Muslims added after the carnage early on Sunday in Orlando.

While the shooting did not alter the poll's night-by-night findings in the presidential race in any significant way, the incident did alter the trend lines on other measures. The proportion of Americans saying the nation is on the right track dropped to 19 per cent from 27 per cent, when compared before and after the Orlando shooting.

BLOOMBERG