UPDATED 7.56am An American election analyst who predicted a Trump win says other pollsters failed to take into account past voting behaviour.

LISTEN ABOVE:  American election analyst Henry Olsen spoke to Mike Hosking

Henry Olsen told Mike Hosking Hillary Clinton's margin was only improving because Mr Trump's supporters were moving into the undecided column.

He used prior election behaviour to predict there'd be a sudden and rapid movement of undecideds and third party voters back to the party of their home.

"The people who said they were going to vote for the Libertarian or said they were undecided were Republican. And I said they're going to come home and vote for Donald Trump, they may not even know it, but they are. That's in fact what happened and that's why Donald Trump won."

Mr Olsen told Mike Hosking people say they're voting for a third party candidate who has no chance of winning - then abandon their vote at the last minute.

"That person may have been lying, or that person may have genuinely been confused, but ultimately decided to come back to the party of their choice."

He said pollsters assume they're being told the truth.

The US Ambassador to New Zealand, Mark Gilbert, says Trump's success comes from a desire for change.

He said there's a trend around the world, that people feel their elected officials don't care, and aren't paying attention to them.

Mr Trump used his victory speech to vow to Americans that he will 'do a great job' as president.

"We must reclaim our country's destiny and dream big and bold and daring."

During his campaign he talked of high tariffs and taxes at the border - but Mr Trump's used his victory speech to address the "world community."

He said while he'll always put America's interests first, he will deal fairly with everyone.

"All people and all other nations. We will seek common ground, not hostility. Partnership not conflict."

He told his supporters it's time to mend the wounds and divisions that've been created throughout the campaign.

Republican house speaker Paul Ryan says Donald Trump's win is the most incredible political feat he's seen in his lifetime.

It seems Mr Ryan wants to let bygones be bygones, congratulating Mr Trump on the win.

Mr Ryan said Donald Trump will lead a unified Republican Government.

"But Donald Trump heard a voice out in this country that no one else heard. He connected in ways with people no one else did. He turned politics on its head."

Mr Ryan said he's promising to work hand-in-hand on the Republican agenda.

"This needs to be a time of redemption, not a time of recrimination. We all need to rededicate ourselves to making America great and making it a more perfect union."

Professor of strategic studies at Victoria University Robert Ayson said Mr Trump will be dealing with a Republican congress, and he'll be able to appoint a Supreme Court justice.

"It's going to be a town that will favour him. There won't be as many checks and balances on him. Mr Obama is a Democrat who's had to deal with a Republican congress."

Professor Ayson said New Zealand's bilateral relationship with America is likely to continue along the same path it's been on under the Obama administration.

"But I think it's not so much what Mr Trump does with the financial relationship with New Zealand. It's how he approaches Asia Pacific affairs, the economic side, trade side, TPP etc.

"There's a sense of uncertainty in terms of how much what he has suggested and promised he will deliver on and how much he will moderate and be moderated by the circumstances."

Mr Trump will be sworn in as President of the United States on the 20th of January next year.