File photo of Donald Trump. (Agence France-Presse)
Billionaire Donald Trump has extended his lead over the Republican presidential field, while Democratic overall frontrunner Hillary Clinton now trails underdog Bernie Sanders in the key early voting state of Iowa, polls showed Thursday.
The results reinforce a steady trend in the 2016 race: with five months to go before the first primaries, political outsiders -- fueled by public anger and impatience with Washington -- are rising up against the race's establishment figures.
That anti-establishment sentiment appears to be hurting Clinton, sitting governors and senators, and dynastic candidate Jeb Bush.
A CNN/ORC poll found Trump surging to 32 per cent support nationally, becoming the first in the broad Republican field to top 30 per cent in the race for the White House.
The brash real estate mogul has gained eight points since August, nearly tripling his backing since shortly after launching his campaign in June.
The poll shows Ben Carson, a retired neurosurgeon, rising 10 points to take second place, with 19 per cent.
Together, these two men -- who have never held public office -- are now backed by a majority of Republicans and Republican-leaning independents, according to CNN/ORC.
A different CNN/ORC poll, also released Thursday, found that Carson now leads Clinton in a hypothetical general election matchup, 51 to 46 per cent, and that Clinton is essentially neck-and-neck with Trump and Bush in a hypothetical face-off.
Bush, former governor of Florida and the son of one president and brother of another, came in third among Republicans in the first poll, with nine percent, a drop of four points since August.
Senator Ted Cruz, widely seen as an outsider and severe critic of the Washington establishment, followed with seven percent, while former Arkansas governor and television personality Mike Huckabee and Wisconsin Governor Scott Walker shared fifth spot at five percent.
Senator Marco Rubio stood at three percent, a five-point slide since August, the polls said.
Staying power In the Democratic race, Sanders nipped former secretary of state Clinton 41 per cent to 40 per cent in a Quinnipiac University Poll of likely Democratic caucus participants in Iowa, which holds the first contest to nominate party flagbearers for the November 2016 election.
The come-from-behind result is the second in a month that shows the independent Sanders surpassing Clinton in a key state.
Last month, he galloped past her in New Hampshire, which holds the first primary after Iowa, to snatch a 44-37 advantage, according to a Franklin Pierce University poll.
The results highlight a surging Sanders while Clinton, dogged by an email scandal, has seen her polling numbers slide in recent months.
Clinton was at 52 per cent in Quinnipiac's July 2 Iowa poll, while Sanders earned 33 per cent.
"Sanders has seized the momentum by offering a message more in line with disproportionately liberal primary and caucus voters," Quinnipiac polling assistant director Peter Brown said.
"He is the candidate of the Democratic left, against his own party's bosses and their prized presidential candidate, Secretary Hillary Clinton."
Nationally, the CNN/ORC poll found Clinton's lead over Sanders has shrunk to just 10 percentage points among Democrats and Democrat-leaning voters, although that was due to losing ground to current Vice President Joe Biden, who is still mulling a potential presidential run, than to a surge by Sanders.
Clinton's favorability rating among Iowa Democrats remains high, at 76 per cent to 20 per cent, with voters saying by a 64-30 per cent margin that she is honest and trustworthy, the poll showed.
That is far better than national polling, in which Clinton's favorability is under water, with just 39 percent viewing her favorably against 51 percent who don't, Quinnipiac reported last month.
Sanders's favorability rating is 78 per cent with six percent against, and 86 percent of voters say he is honest and trustworthy, compared to just four percent who don't believe he is.
Among Republicans, Trump has shown staying power, despite predictions that his star would fade as the primaries near.
Fifty-one per cent of Republican voters now think Trump will emerge as the nominee, compared to the 19 per cent who believe Bush will top the ticket according to CNN/ORC.