U.S. Republican presidential candidate Ben Carson officially ended his bid for the White House on Friday after failing to win any of the early states in the race for the November election.

"There are a lot of people who love me, they just won't vote for me," Carson said in a speech at the Conservative Political Action Conference in suburban Maryland.

Carson had announced on Wednesday he did not see a "political path forward" in his campaign for the party's nomination, and did not attend the Republican debate in Michigan on Thursday.

Carson declined to endorse any candidate for the Republican nomination, though he said he has "talked to all of them this week."

Speaking to the gathering of conservative activists, the retired neurosurgeon said the United States needs "trickle-down ethics." He said the ideal presidential candidate is ethical and accomplished, has clear policies and treats others well. He said whoever can check all of those boxes would be a "great leader."

The conference crowd gave him an adoring standing ovation.

Carson said he will now work on a project to encourage religious values voters to participate in elections.

Carson spent big on consultants

The political newcomer raised $58 million US, more money than any other Republican contender raised.

But an Associated Press review of his campaign finance filings show Carson's campaign is an extreme example of the big-money business of presidential politics. His campaign burned through the millions he raised by spending more on fundraising and consultants than on mass media advertising, on-the-ground employees and other things that could have swayed voters, the filings show.

Over the past week, the candidate himself has wondered aloud whether his campaign aides took advantage of him, even saying he was disappointed in himself for trusting some people around him "without really vetting them carefully."

Carson addressed the issue in an interview with CNN last week and again Thursday in a Yahoo News interview with journalist Katie Couric, who questioned Carson on whether his campaign had spent so much on fundraising to gather a list of donors for a future business venture.

"Mistakes were made," Carson said. "We probably had the wrong team in place, people who probably had different objectives than I did. And once we discovered that and rectified it, the situation changed dramatically."

Some people who worked with Carson's presidential campaign are positioned to continue profiting from his elevated profile even after he officially ends his bid.

All told, the Carson campaign turned over at least one-quarter of the money it raised — $16 million US — to fundraising and marketing firms owned by a pair of his top consultants, Mike Murray and Ken Dawson.

By contrast, the Carson campaign's payroll for nine months cost less than $700,000 US, finance documents show, and the campaign spent less than $600,000 US on television and radio advertising during the month that voting has taken place, according to advertising tracker Kantar Media's Campaign Media Analysis Group.

Murray has been a campaign senior adviser, owns TMA Direct and is managing partner of Precision Data Management, firms that provide fundraising services for direct mail and email to voters and broker lists of would-be supporters.

Dawson has been Carson's unofficial chief marketing officer and owner of Eleventy Marketing. That company uses Facebook, Twitter and other social media to place digital advertising and raise money for its clients.

Murray and Dawson say the payments to their firms do not give a full picture of all the work they did — transforming a candidate with 50 per cent name recognition among likely Republican voters into one who became nearly universally known.

"We had the task of building the Carson brand along with raising money," Murray said. "Everything we did netted money."

Payments to TMA and other firms did not all go into the consultants' pockets, he said. Much of it paid for postage, printing and other costs associated with fundraising. Dawson also said much of the $10 million US paid to his company went right back out to pay for digital advertising and social media promotion.

He said every payment to Eleventy was approved by Carson's campaign managers and audited by campaign staff.

Carson has vowed to continue his "grassroots movement," which includes his 700,000 campaign donors, the majority of whom gave $200 US or less.

With files from Reuters