(CNN) -- Sens. Hillary Clinton and Barack Obama each accused the other of borrowing portions of their presidential campaign speeches Monday.
Massachusetts Gov. Deval Patrick, left, on the stump with Sen. Barack Obama.
The Clinton campaign accused Obama of borrowing from a close supporter, and the Illinois senator responded by saying his own words have been used by Clinton.
On a conference call with reporters, Clinton spokesman Howard Wolfson said it was clear Obama had "lifted rhetoric" from Massachusetts Gov. Deval Patrick.
Late Monday, Clinton followed up with a swipe of her own.
"If your whole candidacy is about words, then they should be your own words," Clinton said in Madison, Wisconsin. "That's what I think."
Obama downplayed the significance of the accusation.
"I've written two books, wrote most of my speeches. So I think putting aside the question ... in terms of whether my words are my own, I think that would be carrying it too far," Obama said.
"Deval and I do trade ideas all the time, and you know he's occasionally used lines of mine," Obama said.
Obama said he also used some of Deval's words at a Jefferson-Jackson dinner in Wisconsin.
"I would add I've noticed on occasion Sen. Clinton has used words of mine as well," said Obama. "As I said before, I really don't think this is too big of a deal."
Obama campaign officials said Clinton had a pattern of borrowing from some of her rival's signature phrases, including "Yes, We Can" and "Fired Up, Ready to Go." They circulated a YouTube video and list of these alleged instances to reporters.
The Clinton campaign earlier pointed to similarities between the words of Obama and Patrick that have raised eyebrows and attracted traffic on YouTube.
A central passage in a speech Obama gave Saturday -- aimed at convincing voters that his campaign is not just about lofty rhetoric -- is adapted from one that Patrick used in his 2006 campaign, the Obama campaign said when asked about it.
The controversy is lost on the Massachusetts governor, who endorsed Obama.
Obama's campaign had Patrick call the New York Times over the weekend and issue a statement.
"Senator Obama and I are long-time friends and allies. We often share ideas about politics, policy and language," Patrick said in the statement. "The argument in question, on the value of words in the public square, is one about which he and I have spoken frequently before. Given the recent attacks from Senator Clinton, I applaud him responding in just the way he did." Watch a comparison of Obama's and Patrick's speeches »
The Obama campaign also confirmed comments chief strategist David Axelrod -- an adviser on Obama's Senate campaign and Patrick's gubernatorial run -- made to the New York Times about the speeches.
"They often riff off one another. They share a world view," Axelrod told the Times about Obama and Patrick. "Both of them are effective speakers whose words tend to get requoted and arguments tend to be embraced widely."
Responding to attacks from Clinton that he offers words while she offers action, Obama has been arguing that words matter.
Saturday night at a gala for the Wisconsin Democratic Party, Obama said to frequent applause, "Don't tell me words don't matter! 'I have a dream.' Just words. 'We hold these truths to be self-evident, that all men are created equal.' Just words. 'We have nothing to fear but fear itself.' Just words, just speeches!"
In 2006, Patrick, fending off attacks from his rival Kerry Healey, told a crowd, "Her dismissive point, and I hear it a lot from her staff, is all I have to offer is words. Just words. 'We hold these truths to be self-evident, that all men are created equal' -- just words. Just words. 'We have nothing to fear but fear itself' -- just words. 'Ask not what your country can do for you, ask what you can do for your country' -- just words. 'I have a dream' -- just words."
Speaking last week at a General Motors plant in Ohio, she said, "There's a big difference between us -- speeches versus solutions, talk versus action. You know, some people may think words are change. But you and I know better. Words are cheap. I know it takes work." E-mail to a friend
CNN's Josh Levs, Rebecca Sinderbrand and Chris Welch contributed to this report.