Two head-to-head polls released today showed a resurgent Hillary Clinton vaulting atop the US presidential race after a tumultuous month for Donald Trump, who has failed to rally confidence among voters or party leaders.
A Washington Post-ABC News poll showed a 12 percentage point lead for the Democrat, her largest advantage since the last northern autumn and a dramatic improvement over last month when the poll showed her statistically tied with Trump.
If the presidential election were held today, 51 per cent of respondents said they would vote for Clinton, versus 39 per cent for Trump.
However, a Wall Street Journal/NBC News poll showed a slimmer lead for Clinton, 46 per cent to Trump's 41 per cent.
They were essentially tied, 39 per cent for Clinton and 38 per cent for Republican opponent, when third-party candidates were included, this poll showed.
The surveys come after a difficult month for the combative Trump, a political novice who fired his campaign manager and faced criticism for poor campaign organisation and a paltry war chest of US$1.3 million at the end of May.
Clinton, who has repeatedly pounded Trump as being "temperamentally unfit," finished the month with US$42 million.
Trump faced a widespread outcry after he accused a federal judge of bias because of his Mexican heritage. The judge is presiding over cases involving Trump's defunct online university.
And in the aftermath of the mass shooting at a gay nightclub in Orlando, the brash businessman tweeted his thanks to people who congratulated him for "being right on radical Islamic terrorism."
He renewed calls for a temporary ban on Muslims entering the United States and then doubled down, suggesting profiling of Muslims was not off the table.
At the weekend, Trump seemed to change course, saying immigration from "regions linked with terrorism" should be suspended.
"I think there's no question that he's made a number of mistakes over the last few weeks," Republican Mitch McConnell, the Senate majority leader, told ABC News.
"I think they're beginning to right the ship. It's a long time until November. And the burden, obviously, will be on him to convince people that he can handle this job."
According to the Washington Post-ABC News poll, two in three Americans say Trump is unqualified to lead the nation, are anxious about the idea of a Trump presidency and find his comments about women, minorities and Muslims to show an "unfair bias".
However, survey respondents also indicated unease with former Secretary of State Clinton.
A majority disprove of the way Clinton has handled questions over her use of a personal email server during her tenure as the nation's top diplomat, and half are anxious about the idea of her in the White House.
Although Clinton's rival for the Democratic nomination, Bernie Sanders, has yet to officially drop out of the race and endorse her, the Wall Street Journal/NBC News poll showed 78 per cent of his primary supporters backed her.
Speculation continued to swirl about who will be the running mates of the two presumptive nominees.
Former Republican House Speaker Newt Gingrich, whose decades of political experience would be a counterbalance to Trump, has been repeatedly mentioned as a potential vice presidential candidate but said today he has not been contacted about the position.
He said he thinks Trump will make a last-minute decision even though the start of the Republican National Convention in Cleveland is just over three weeks away.