A Fox News poll found Donald Trump losing the presidential election to the top four Democratic contenders - Joe Biden, Elizabeth Warren, Bernie Sanders and Kamala Harris.

Biden did the best against the president, beating 50 per cent to Trump's 38 per cent.

In the rest of the head-to-head matchups, Trump came in at 38 per cent to Sander's 48 per cent, Warren's 45 per cent, and Harris' 46 per cent.

It marked the first time Warren and Harris topped Trump in the poll.

Donald Trump lost to the top four Democratic presidential contenders in a Fox News poll

'Biden and Sanders have held sizable leads over Trump before,' Democratic pollster Chris Anderson, who conducts the Fox News Poll with Republican Daron Shaw, told the network. 'But this is the first time our poll results give Warren and Harris the chance to stake a claim to an electability argument as well.'

Also, in the poll, 52 per cent said they disapproved of Trump's response to the recent mass shootings in El Paso, Texas, and Dayton, Ohio.

And 59 per cent said they were not satisfied with the way things are going in the country.

The Fox News poll was taken between August 11-13 and contacted 1,013 registered voters on landlines and cellphones. The margin of error is plus or minus 3 percent.

The numbers come after the president went after his rivals in a campaign rally in Manchester, N.H., on Friday night.

He unleashed a wave of fury on Warren, whom he called 'Pocahontas,' and 'Sleepy Joe Biden', while mocking the former vice president's small crowds and lagging campaign schedule.

'What about a Sleepy Joe Biden rally? Right? Boy, he's made some beauties. I sort of hope it's him. I don't mind any of them. You got Pocahontas, who's rising. You've got Kamala. Kamala is falling,' he said.

The president was more gung-ho about hitting his Democratic opponents than at recent rallies. He started in on them from the outset.

'One of them has a rally, he's got 100 people,' he claimed, meaning Biden. 'So this holds 12,000 people. We're full. And we could fill it up four times, at least.'

The president speculated that he'd be able to beat anyone in the general election the other side puts forward.

'I don't know that it matters. But whoever it is, different, different people. But I don't know, I think Sleepy Joe may be able to limp across the finish line. Might be.'

He made reference to a report in The Hill on Thursday that said Biden's team is looking to scale back the candidate's schedule to cut down on the amount of gaffes the 76-year-old makes after a long day of campaigning.

'But today they announced that they're going to cut way back on his appearances because he is such a disaster they're going to have fewer appearances,' he claimed. 'You heard this, right? They're going to cut way back on his appearances. Can you believe it?'

He assessed, 'If I ever did that, it would be over! The fake news would get us. And we don't let them get us. And it is fake.'

Joe Biden and Bernie Sanders have beaten Trump in polling before but this marks the first time Elizabeth Warren and Kamala Harris have topped the president in the Fox poll

Trump called Democrats seeking their party's nomination 'a group of socialists or communists' minutes later - 'could be, they're not far away' - and asked his supporters if they want to pay a '95 percent tax rate,' which is something that no presidential candidate has proposed.

'Does anyone want pay 95 percent tax in the room? I don't think so,' he said in the 'Live Free or Die' state to loud booing.

He took a shot at the progressive Green New Deal, as well, saying, 'It's a beautiful thing. We want it to continue onward, until a month before the election.'

Warren is also being giving a pass, for now, he said, promising to resuscitate the attack on her heritage down the line.

'I did the Pocahontas thing. I hit her really hard. It looked like she was down and out,' he said. 'That was too long ago. We should have waited.'

He added, 'But don't worry it can be revived. And we're going to have some fun in the state of New Hampshire.'