Massachusetts Senate Candidate Elizabeth Warren (D) published an op-ed today criticizing her opponent, Sen. Scott Brown (R), for his opposition to the Buffett Rule, a proposal by the Obama administration to implement a 30 percent minimum tax on millionaires. She also took a swipe at GOP Presidential hopeful Mitt Romney, calling his ability to pay a lower tax rate than many middle-class working families wrong and unfair. “Just last week, Scott Brown said in an interview that he thinks Mitt Romney and Warren Buffett should get special tax breaks that are not available to most Americans. I don’t think that’s fair,” wrote Warren. Brown, who now trails Warren in most polling, told The Sun Chronicle last weekend that he opposes Obama’s plan.