(CNN) – Battling to keep his seat Tuesday, Republican Sen. Scott Brown of Massachusetts called on his Democratic challenger Elizabeth Warren to release six years of tax returns. And she responded announcing she would instead release four years' worth.
Brown's campaign manager Jim Barnett sent a letter to Warren's campaign, saying the senator will make public his returns from 2006 to 2011 and urged Warren to do the same.
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"You have offered to release far more limited information, and even then have made that contingent on a demand that Senator Brown go first," Barnett wrote in the letter addressed to Warren. "The people of Massachusetts deserve better from their candidates for Senate than the type of political gamesmanship you are engaging in."
Responding to the letter, Warren's campaign said they plan to release four years of returns on Tuesday, besting Brown's release date of Friday by two days.
"Elizabeth Warren has been clear from the beginning that she would voluntarily release her tax returns, and she is glad to see that Republican Senator Scott Brown has finally agreed to do the same. Elizabeth is not a career politician like Senator Brown, but she will release her tax returns for her entire time in public service and by releasing 4 years of returns, she is providing the people of Massachusetts with a transparent and full accounting of her financial situation," her spokeswoman, Alethea Harney, said in a statement to CNN.
The move came after The Boston Globe requested both candidates release last year's returns, as well as the five prior to that.
According to the Globe, Warren had initially agreed to release two years, which would cover the time she served as an adviser to the president during the formation of the Consumer Financial Protection Bureau.
Brown's campaign argues six years of returns from Warren would reveal further details about the candidate's six-figure salary as a Harvard law professor, as well as any additional outside legal work.
"Now, as a candidate for U.S. Senate, you have an opportunity to demonstrate that your rhetoric on transparency is more than sanctimony," Barnett said in the letter.
Warren's campaign did not immediately respond to request for comment.
The recent spat marks another sign of the race shaping into a competition over who can be the candidate with the most middle class appeal.
Last week, Brown knocked his opponent as "elitist" and "hypocritical" for declining to pay the elective higher tax rate in the state of Massachusetts, despite her advocacy for the so-called Buffett Rule–a White House proposal that calls for millionaires to pay a higher tax rate.
Very few taxpayers choose to pay the optional rate in Massachusetts, however. According to Bob Bliss, communications director at the state's revenue department, less than 1% of taxpayers paid the rate of 5.83%, slightly higher than the normal tax rate of 5.3%.
Responding to Brown's criticism on the optional tax rate, the Warren campaign argued the point of the Buffet Rule is for everyone to play by the same rules, not arbitrary or voluntary rules.
"The Buffet Rule is about making sure millionaires and billionaires pay their fair share, not about funding government through voluntary contributions. This question misses the key point in the debate, because it's not just about economics but about our values," Harney told CNN on Friday.