President Donald Trump. Getty Images President Donald Trump's approval rating has fallen to 37% — a new low, according to a Quinnipiac University national poll released Wednesday.

The poll found the president to be losing crucial support among Republicans, men, and white voters.

The survey of 1,056 voters from across the US found that Trump's approval among Republican voters dropped to 81%, from 91% of those surveyed in a similar Quinnipiac poll two weeks ago. His disapproval rating among that group jumped to 14% from 5%.

The poll showed those in Trump's most supportive demographics — male and white voters — to be increasingly unhappy with his performance. Forty-three percent of men approved of Trump — down from 49% in the most recent poll, while 44% of white voters approved, also down from 49%.

"Most alarming for President Donald Trump, the demographic underpinnings of his support, Republicans, white voters, especially men and those without a college degree, are starting to have doubts," the assistant director of the poll, Tim Malloy, said in a statement.

A large majority of those polled — 70% — did not believe Trump's unsubstantiated claims from Twitter that President Barack Obama wiretapped his phones before the 2016 election. The administration has continued to stand by the accusation, even after FBI Director James Comey told Congress on Monday that the FBI had "no information" to support it.

Seventy-three percent of voters said Trump and his administration made statements without supporting evidence "very often" or "somewhat often."

Voters also showed increasing doubt in Trump's honesty and leadership. Sixty percent of respondents thought Trump was dishonest, compared with 55% in the March 7 poll, and 57% thought he didn't care about average Americans.

Trump has denounced low approval ratings as "fake news" and dismissed polls in January that showed he would be the lowest-rated incoming president in modern history. The Real Clear Politics average of 11 major polls puts Trump's approval rating at 42.8% and his disapproval rating at 51.3%.

The Quinnipiac survey released Wednesday had a margin of error of plus or minus 3%.