Evangelical support for Donald Trump has not wained despite the threat of impeachment hanging over the US President. 

In a survey by the Public Religion Research Institute (PRRI), more than three quarters (77%) of white evangelical Protestants said they approved of the job Trump was doing in office, including half (50%) who strongly approved. 

Support for Trump rose among Republican-voting white evangelicals, with 82% saying they preferred him to be their party's nominee. This was significantly higher than Republicans identifying as white mainline Protestants (75%), white Catholics (73%) and the religiously unaffiliated (65%). 

By contrast, only 39% of respondents overall said they approved of the job Trump was doing as president. 

PRRI interviewed 2,527 Americans for the study, with 343 survey respondents describing themselves as white evangelical Protestant.

White evangelicals were more likely than any other religious demographic to say that Trump's personal conduct did not affect the likelihood of voting for him, with nearly half (47%) saying it "does not make a difference" in their support for him. 

Only 36% of white evangelicals said his conduct made them less likely to support him, and 16% said it actually made it "more likely" that they would support Trump.

This different significantly from 62% of all respondents who said that Trump's personal conduct and behavior made them less likely to support him.

Support for Trump dropped significantly among ethnic minority Christians, with only 28% of Hispanic Catholics saying they approved of Trump's job performance. Similarly, 86% of black Protestant respondents and 81% of religiously unaffiliated respondents said they disapproved of his performance as president.

"I think that the data here shows that [Trump's] support among evangelicals is not just rock-solid, it is growing if you look at several years PRRI data here," said PRRI Board Chair Melissa Deckman, professor of public affairs at Washington College in Maryland.

"Although this wasn't broken down among religious tradition, I thought one of the most telling figures in the analysis was that 94% of Republicans believe that their party is trying to protect the American way of life from outside influence.

"I think evangelicals continue to back Donald Trump because they view him as their champion. He has delivered on many policies that other Republican presidents haven't."