Almost two-thirds of white evangelical Protestants in the US believe “their side” is winning politically under the Trump administration, according to a new survey.

The proportion has increased steadily during Trump’s presidency. In May 2016, six months before he was elected, 23% of white evangelical Protestants said their side was winning politically, rising to 36% two years ago, and 63% last month.

The survey, published by the Pew Research Center on Thursday, found that a big majority of white evangelical Protestants in the US – a key part of Trump’s electoral base – believed the president was good for their interests, but they had more mixed views on his personal attributes.

More than eight in 10 said the Trump administration “fights for what I believe in” either very or fairly well. But markedly fewer – 61% – said the phrase “morally upstanding” described the president very or fairly well.

“Even among this strongly supportive constituency, most do not view Trump as a very religious, honest or morally upstanding person,” said the report.

In more general terms, 63% of both all US adults and white evangelical Protestants said it was very important to them to have a president who “personally lives and moral, ethical life”.

Almost half - 49% – of all US adults said the Bible should influence the laws of the country, a proportion which rose to 89% among white evangelical Protestants.

One in 20 US adults believe that “God chose Trump because God approves of Trump’s policies”, rising to 13% among white evangelical Protestants.

“Across all religious groups in this analysis, there is near consensus on one Trump characteristic: majorities of all groups, including 70% of white evangelicals, say that ‘self-centered’ describes Trump at least fairly well,” the report said.

In general, 83% of white evangelicals identify with or lean towards the Republican party, the survey found. White evangelical Protestants form 16% of the US population, Pew found last year.

Pew questioned almost 6,400 US adults last month.