Meredith McIver, a staff writer for the Trump Organization, said she had inserted passages into Melania Trump's speech that resembled parts of a 2008 speech by first lady Michelle Obama.
“I did not check Mrs. Obama’s speeches. This was my mistake and I feel terrible for the chaos I have caused Melania and the Trumps, as well as to Mrs. Obama. No harm was meant,” McIver said in a statement.
She said Melania Trump had read passages from Michelle Obama’s speech to the 2008 Democratic National Convention over the phone to her as examples. McIver then wrote them down and later included some of the phrasing in a draft that became Melania Trump's speech on Monday night.
The accusations of plagiarism cast a shadow over Republicans' attempts to mount a smooth convention in Cleveland this week and present Trump to voters as a job creator and a strong hand on national security, immigration and violent crime.
Democrats said the Monday night affair and the Trump campaign's various explanations over the next 48 hours showed his team was not ready for prime time, all the more embarrassing because Trump has accused the presumptive Democratic nominee Hillary Clinton of being untrustworthy.
In his first comments addressing the speech controversy, Trump argued early on Wednesday that the fuss could in fact be a plus for his campaign.
"Good news is Melania's speech got more publicity than any in the history of politics especially if you believe that all press is good press!" Trump wrote on Twitter.
In a potentially embarrassing admission for the Trump campaign, speechwriter McIver said in her statement that Michelle Obama is a person that Melania Trump "has always liked.”
A small section of Melania Trump's roughly 15-minute speech, a highlight of the opening day of the convention in Cleveland, was similar to Michelle Obama’s 2008 speech in support of Barack Obama, then a U.S. senator campaigning for president.
Under pressure to explain what had happened and who was to blame, Trump's people offered different versions of events on Monday and Tuesday.
Hours before giving the speech on Monday, Melania Trump told NBC's "Today" that she wrote it with as little help as possible. But her husband's campaign manager, Paul Manafort, told CBS' "This Morning" on Tuesday that it was a collaboration with speechwriters.
McIver said Trump and his family rejected an offer from her to resign after the speech controversy broke. The Trump Organization is owned by Donald Trump.
Trump planned to make a display of solidarity on Wednesday with his running mate, Indiana Governor Mike Pence, a social conservative who is at odds with the New York businessman on many issues. Pence is the keynote speaker on Wednesday, the third day of a convention that ends on Thursday night when Trump accepts the nomination.