In Massachusetts Senate Race, Elizabeth Warren and Scott Brown Trade Jabs Over Taxes BOSTON - It has been a week of tax wars for Senator Scott P. Brown of Massachusetts and his presumed Democrat opponent, Elizabeth Warren. Ms. Warren, a Harvard professor who gained a national following as a consumer advocate, has hammered Mr. Brown for opposing the "Buffett Rule," which would increase taxes on the nation's richest households. He has sought to reframe the debate by asking whether Ms. Warren voluntarily paid a higher state income tax rate, which is an option in Massachusetts. Ms. Warren did not answer the question until Friday, when, in response to a reporter's question during an event at her campaign headquarters, she acknowledged that she had not paid the optional higher rate. "I paid the taxes that are legally owed," she said. I did not make a charitable contribution to the state. She added: "Scott Brown just voted against the Buffett Rule and he's trying to find some way to change the conversation from that. But no matter how many times he says it, he cannot avoid the fact that on the fundamental question of whose side are you on, he stands with people making a million dollars a year or more paying lower tax rates than secretaries. I think he's wrong. Mr. Brown's camp quickly shot back. "The problem with running a campaign based on self-righteousness and moral superiority is that you had better live up to the same standard you would impose on everyone else," said Jim Barnett, Mr. Brown's campaign manager. He added that Ms. Warren "lectures others about their obligation and responsibility to pay higher taxes, but she refuses to pay the optional higher rate available in Massachusetts." An attempt by Senate Democrats to pass the Buffett Rule failed Monday on a procedural vote, with Mr. Brown joining all but one other Republican, Senator Susan Collins of Maine, in voting not to open debate on the measure. It would have required anyone earning $1 million or more a year to pay a 30 percent tax rate. Mr. Brown called it a gimmick that would provide negligible revenue. Ms. Warren held a news conference on Friday with former Senator Russell Feingold, a Democrat from Wisconsin, to call for legislation that would require more disclosure from "super PACs" and other big donors. But the questions from reporters focused on Ms. Warren's taxes, including whether she would release her tax returns. The Boston Globe asked Ms. Warren and Mr. Brown earlier this week to release six years of their tax returns. Ms. Warren has said she would release her returns from the last two years if Mr. Brown did the same. Mr. Brown has hinted he would go further, but has not committed yet. Mr. Brown has already revealed in federal personal disclosure forms that he earned a $700,000 advance on his memoir in 2010; the Center for Responsive Politics has put his assets at between about $1 million and $2.3 million. Ms. Warren's forms show that she owns stock and other investments worth more than $3 million.