Odd couple: Bernie Sanders and Donald Trump lead in early-voting US state
Democratic Presidential Hopeful Senator Bernie Sanders (I-VT) speaks with students during an event in Washington, DC, June 4, 2015 (AFP Photo/Saul Loeb)

Wealthy magnate Donald Trump and anti-billionaire Bernie Sanders are political opposites united in their outsider status in the presidential race -- and each leads his party in the polls in early-voting New Hampshire.

Both candidates have overshadowed their White House rivals on both sides of the political divide, by tapping into voter resentment with Washington, suspicion of the establishment and a deep appreciation of underdog candidates who can shake up a presidential contest.

This is not the way the political establishment envisioned the 2016 race.

Trump, the brash billionaire real-estate tycoon, tops the latest Franklin Pierce University/Boston Herald poll with 18 percent support from Republican New Hampshire voters, following his contentious performance in last Thursday's first major Republican debate.

Former Florida governor Jeb Bush came second with 13 percent.

A CNN/ORC poll released Wednesday shows Trump ahead with 22 percent support in Iowa, another crucial early-voting state, and neurosurgeon Ben Carson, also a political novice, in second with 14 percent.

Meanwhile Sanders, a self-described democratic socialist, surged ahead in the Democratic race in New Hampshire, snatching a 44 percent to 37 percent lead advantage over Hillary Clinton, according to the Franklin Pierce survey.

While the former secretary of state is still overwhelmingly seen as the likely nominee, and leads in national polls, it marks the first time she has trailed anywhere in the primary race.

"It shows that voters are very much looking for something different, and that there is a lot of frustration on the right and left in American politics," Brown University political science professor Wendy Schiller told AFP.

"The same old establishment answers are not, at the moment, good enough."

And so voters are turning away from another possible Bush-Clinton matchup, instead propelling outsiders who are populists in their own different ways.

- Playing off each other -

Trump is the impeccably dressed, free-market prince who exults in his financial success, an improbable candidate who denounces rivals and leaders in Washington as "idiots," but who has yet to lay out policy details of his own.

Sanders, the disheveled independent senator who rails against the rich and the "oligarchy" fueled by runaway campaign spending, blasts grotesque income disparity and a looming Pacific trade deal.

While their platforms could not be more different, they have a similar appeal, according to Schiller.

"I see them exerting equal kinds of influence on their parties, especially on the prospects of registering more voters," she said.

"Sanders and Trump play off each other, and they're bringing a lot more people into the political system."

Vermonter Sanders may ultimately be serving a more vital role, Schiller argued.

He will push the Democratic Party "to reaffirm its commitment to core liberal values," she said.

This includes providing for the most vulnerable, reforming campaign finance laws and expanding health care.

Trump, while firing up a conservative base furious with Washington, could alienate some voters with his aggressive temperament, evident when he made crude remarks about a female Fox News debate moderator.

He has also sent confusing signals to Republicans.

Trump says he has "evolved." But in the past he was registered as a Democrat, backed the Clintons, supported abortion rights and some form of universal health coverage, and called for a huge one-time tax on the wealthy.

Whether Trump and Sanders will be able to convert the early enthusiasm and poll numbers into actual votes on election day remains the potent question.

Meanwhile Sanders is drawing the largest crowds of anyone on the 2016 campaign trail, including 28,000 on Sunday in Oregon and nearly as many Monday in Los Angeles.

The Donald, as he is nicknamed, could not help but slam Sanders Tuesday when asked about a recent rally that Sanders abandoned after protesters jumped the stage and took the microphone.

"I felt badly for him. But it showed that he's weak," Trump sneered.

"He's getting the biggest crowds and I'm getting the biggest crowds, but believe me, that's not going to happen to Trump."