A new poll in the US shows a surge in national support for the presumptive Republican presidential candidate Donald Trump against Democratic frontrunner Hillary Clinton.

The Reuters/Ipsos poll released on Wednesday shows 41 percent of respondents supported Clinton while 40 percent backed Trump, with 19 percent undecided yet.

This is while as recently as last week, Clinton led Trump by some 13 points in a previous poll.

The latest online poll of 1,289 people conducted from Friday to Tuesday reveals the dramatic turnaround since Trump became the Republican Party's presumptive nominee.

Trump has briefly matched Clinton’s support a few times this year, most recently in mid-March, after US Senator Marco Rubio of Florida dropped out.

US presidential elections are decided by the Electoral College, based on state-by-state results, and not through the national popular vote.

Opinions may change ahead of the November 8 presidential election as American voters become inundated with hundreds of millions of dollars in campaign advertising, highly publicized debates and a pair of party conventions.

A recent Reuters/Ipsos poll found that a majority of voters did not trust either candidate with key presidential responsibilities such as managing the US economy or handling the role of commander in chief.

Also, nearly half of people, 47 percent, said they were "scared" that Trump has become the presumptive GOP nominee, while 26 percent said they were "hopeful," according to an NBC News/Survey Monkey poll of voters released Tuesday.

More people are scared than hopeful about Clinton becoming president as well. Thirty-five percent reported being "scared" if Clinton were to win the Democratic nomination, while 29 percent would be hopeful, 22 percent would be angry, 16 percent would be excited and seven percent would be surprised.