Mitt Romney says President Barack Obama won re-election last week because of the "gifts" he had provided to blacks, Hispanics and young voters and because of his effort to paint Mr Romney as anti-immigrants.
"The president's campaign, if you will, focused on giving targeted groups a big gift," the defeated Republican presidential challenger said in a phone call with top donors.
He cited immigration proposals aimed at Hispanics and free contraception coverage that appealed to young women. "He made a big effort on small things."
Mr Romney said his campaign, in contrast, had been about "big issues for the whole country."
White House press secretary Jay Carney disputed Mr Romney's assessment, telling reporters travelling with Mr Obama aboard Air Force One that policies allowing more young people to go to college or stay on their parents' health plans are good for all Americans and the economy as a whole.
"I think that view of the American people or the electorate and the election is at odds with the truth of what happened last week," Mr Carney said.
Mr Romney also did not acknowledge any major errors and said his team had run a superb campaign.
By contrast, many Republicans are questioning their strategy after Mr Obama's strong win, with some saying they must reach out to Hispanics and others as their core demographic, ageing white males, shrinks.
Growing numbers of Hispanic, black and young voters overwhelmingly voted Democratic last week.
Top Republicans meeting for the first time since the election said the party lost its bid to unseat Mr Obama because Mr Romney did not respond to criticism strongly enough or outline a specific agenda with a broad appeal. Many had assumed that an election with the struggling economy as the top issue would favour a businessman like Mr Romney, but he was weakened by his constant shifting on sensitive social issues like abortion.
In conversations at the Republican Governors Association meeting in Las Vegas, a half dozen party leaders predicted the Republicans will lose again if they keep running the same strategy.
"We need to have a brutal, brutally honest assessment of everything we did," said Haley Barbour, the former Mississippi governor who is widely seen as one of the Republicans' sharpest political operatives.
"We need to take everything apart ... and determine what we did that worked and what we did that didn't work."
