The courts are one of the most difficult institutions for a President of the United States to change, but Donald Trump does have some opportunities to do so, according to David Frum, a former speechwriter for George W Bush.

Mr Trump's attacks on the judiciary have caused concern in recent days, as he has personally criticised judges who are expected to rule impartially on his executive order on immigration.

Mr Trump's real job, though, is to avoid the courts if he can, said Mr Frum.

"There are about 900 federal judges — Article III judges we call them — who are confirmed by the Senate in three layers of courts — the Supreme Court, the Appellate Court and the District Court," he told Lateline.

"There are a very high number of vacancies on those courts, over 100, so Donald Trump will be able to fill those vacancies."

Mr Frum, now a senior editor at The Atlantic, said because judge nominations needed Senate approval "you can't just put any old person on a federal court".

"[Mr Trump's] job is to stay out of court, to defeat the courts, by avoiding them, and that means dealing with his greatest risk which is Congress, and there he is more successful on neutralising the checks and balances."

'A lot of stops before Hitler station'

While Mr Trump's critics have compared him to fascists and communists, Mr Frum said "history doesn't repeat itself that way".

"The train by which the democratic government goes wrong has a lot of stops on it before it reaches Hitler station," he said.

"We're not going to have those kinds of highly ideological totalitarian dictatorships in the 21st century. But what we do see all around the world is a corrosion of democratic institutions.

"We've seen South Africa post-Mandela sliding away from democratic ideals. We've seen what's happening in the Philippines. Hungary is a tragic example on the European continent. Poland seems to be following Hungary, some of the smaller south European states like Slovakia and Croatia seem to be going down that path. And France may follow after the elections in the Spring.

"Highly advanced democracies are not immune to the populist authoritarian strains that have over taken the newer democracies. We're very arrogant about it but our arrogance is ill founded.

"We are vulnerable to those same tendencies because we are so confident nothing wrong, nothing too serious can happen to us, that we don't maintain our civic institutions in the way they need to be maintained.

'Neutralising the press'

Sorry, this video has expired David Frum says Donald Trump is trying to "neutralise" the press by depriving them of their audience.

More untruths have come from the White House in the past two weeks than in the previous 25 years, according to Mr Frum.

"We have seen a great deal of the President's effort has gone into neutralising the press, not by censoring them, but by depriving them of their audience, by filling the air with so many lies that people no longer believe there is such a thing as truth any more," he said.

And he said there had never been anything like the press conferences hosted by White House press secretary Sean Spicer.

"It's really amazing that things are said from that podium in front of the White House insignia that are not true.

"Press secretaries are not under oath and have a long history of misleading or evading the question ... but they do not outright lie.

"What has happened in the last two weeks represents more untruths that have come from that podium in the previous quarter century. There's nothing like it."

He said more and more people in the US Government have been drawn into "the production of an alternative reality, or alternative facts, that are designed to create cynicism".

"Instead of asking them to believe anything, it's better to ask them to believe nothing. Because then they can't ever say you lied to them. They expect to be lied to."