Conservative Christians will gain influence under Donald Trump's presidency, more than half of Americans believe.

According to a Pew Research study released this week, 52 per cent of Americans believe this will be the case, while just 15 per cent think conservative Christians will lose influence under Trump's administration.

Trump, who will be inaugurated as President of the United States during a ceremony in Washington today, has repeatedly promised to protect Christians – a line that played well with his evangelical audience.

More than 81 per cent of white evangelicals voted for the New York billionaire in the November 7 election.

More than half of people (51 per cent) surveyed by Pew said white people would gain influence with Trump as president.

Black people, meanwhile, were expected by just 19 per cent of people to gain influence.

A majority (56 per cent) believed hispanics would lose influence under Trump's administration – and almost the same number said the same of poor people (55 per cent) and gays and lesbians (54 per cent).

"The public's assessments of the groups that will gain and lose influence in Trump's presidency are sharply different than before Barack Obama took office eight years ago." Pew said.

"In many cases, they mirror views of expected 'winners' and 'losers' under George W Bush before he took office in January 2001."