President Donald Trump's approval rating hit 50 percent Friday in one major national poll for the first time since last June.

The Rasmussen Reports daily tracking poll shows half of all Americans say Trump is doing a good job in office, while 49 per cent disagree.

The president spent most of his first two months in office polling above 50 per cent, but a steady drumbeat of criticism and suspicion related to a trio of Russia investigations has dragged his numbers down.

Yet the president's popularity has been buoyed by December's tax cut package, especially as Americans begin to see results in their paychecks.

Trump's numbers in the Rasmussen poll have only been in the 50-plus territory on 14 per cent of his days in office.

President Donald Trump has hit 50 per cent in Rasmussen's daily presidential approval tracking poll

The last time Trump was at 50 per cent was in the middle of June 2017

Barack Obama polled better than 50 per cent 27 per cent of the time while he was commander-in-chief.

Of the national polls that sampled Trump's job approval in the past month, the Rasmussen survey is the only one that sampled 'likely voters.'

The others broadened their samples to include 'registered voters' – whether or not they plan to cast ballots in the future – and, in some cases, Americans at large.

An average of polls maintained by Real Clear Politics shows that Trump's overall rating during the past two weeks is 42.2 per cent.

Trump's current level of support is also above his performance level in the 2016 election, when 46.1 per cent of voters chose him over Hillary Clinton and a handful of minor candidates.

Obama began his presidency at 67 per cent approval in the Rasmussen tracking poll, compared with 56 per cent for Trump.

Barack Obama polled better than 50 per cent 27 per cent of the time while he was commander-in-chief – nearly twice Trump's rate so far

Trump has been fighting off a collection of political headaches, including a special counsel probe into whether his campaign colluded with Russians who aimed to meddle in the 2016 election.

Nearly 20 women have accused him of some level of sexual harassment or abuse, depressing his support among female voters.

The president has also been plagued by far greater turnover of senior staff than his predecessors, most recently losing his staff secretary following domestic violence accusations from two ex-wives.

The instability of Trump's inner circle hasn't projected strength: Departures of his initial chief of staff, chief strategist, press secretary, health secretary, national security adviser, FBI director and a pair of communications directors have all been public-relations train wrecks.

And Omarosa Manigault-Newman's ouster from the Office of Public Liaison led her back to reality television, where she trashes the administration at every turn.

The Rasmussen poll is clearly an outlier among recent surveys, but it's also the only recent poll to sample 'likely' voters

The Rasmussen Reports national poll was among the few that came closest to accurately predicting the results of the election that vaulted Trump to power.

Unlike other polls that ask questions in live telephone interviews, it relies on push-button phone calls – meaning voters who like Trump's performance in office aren't required to say so out loud to another person.

Some political scientists have called the result 'The Trump Effect,' a phenomenon that explained how social distaste for the president might depress his numbers in polls that use live operators.