Donald Trump narrows Hillary Clinton gap to just six points: poll
US presidential candidate Donald Trump, pictured on August 17, 2015 in New York City, is growing increasingly competitive in a general election match up against Hillary Clinton (AFP Photo/Don Emmert)

Real estate mogul Donald Trump is growing increasingly competitive in a general election matchup against Hillary Clinton, trailing the Democratic frontrunner by six points in a Wednesday poll that shows the race tightening.

Trump leads the broad Republican field by double digits. The political neophyte has dominated media coverage since he launched his campaign in June, steadily narrowing the gap against Clinton, according to a CNN/ORC poll which has tracked such matchups for months.

Clinton now leads Trump by 51 percent to 45 percent, a dramatically more competitive race than July's 56-40 spread and June's 59-35, the poll results showed.

The poll also has her ahead of conservative Wisconsin Governor Scott Walker by the same margin, while she leads former Florida governor Jeb Bush by nine points and Hewlett-Packard former chief executive Carly Fiorina by 10 points.

Trump registered gains among Republicans and Republican-leading independents, whose support surged from 67 percent in July to 79 percent now; men (from 46 percent in July to 53 percent now); and white voters (from 50 percent to 55 percent).

The results show the bombastic billionaire is not just resilient in the early stages of the race -- he is improving his standing despite constant controversy.

He has been criticized for several brash statements, toxic criticism of his rivals and a plan for mass deportations of undocumented immigrants that a New York Times editor called "idiocy."

While Trump gains, Clinton's fortunes have slipped.

Democratic voters still have her leading in their party's nomination race, but with just 47 percent support, down nine points since July and the first time her backing has dropped below 50 percent in CNN/ORC national polling on the 2016 presidential race.

Liberal US Senator Bernie Sanders is second with 29 percent -- a surge of 10 points since July.

Vice President Joe Biden, who is not officially a candidate but is mulling jumping into the race, is third with 14 percent.

That support would likely migrate to Clinton if he does not run, but the poll showed that 53 percent of Democrats and Democratic-leaning voters say they believe the vice president should throw his hat in the ring, while 45 percent say he should not.

Former Maryland governor Martin O'Malley has two percent support, while the remaining two Democrats have one percent or less.

While Clinton maintains the Democratic edge, the positive impressions of her are fading, driven largely by concern over the lingering scandal about her use of a private email account and private server while secretary of state.

The poll shows 44 percent of respondents hold a favorable view of her, compared with 53 percent unfavorable, her lowest rating since 2001, according to the poll.

In March, her favorability rating was 53-44.