Washington (CNN) Mitt Romney's personal aide is disputing a claim by one of President Barack Obama's top campaign strategists that Romney implied during his concession call that Obama won the 2012 election just because he turned out the black vote.

The claim, stemming from the election-night phone conversation between the two candidates, surfaced in a new book by David Axelrod, Obama's political adviser and message guru.

Obama was "unsmiling during the call, and slightly irritated when it was over," Axelrod writes, according to the New York Daily News , which obtained an advance copy.

"'You really did a great job of getting the vote out in places like Cleveland and Milwaukee,' in other words, black people,'" Obama said, paraphrasing Romney. "That's what he thinks this was all about."

Obama's 2012 campaign manager, Jim Messina, backed up Axelrod's story in a tweet Thursday.

Every word of @davidaxelrod mitt e-night call is true. I was standing with axe & POTUS. That's what happened. — Jim Messina (@Messina2012) February 5, 2015

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