Democrats cast it as a bid for fairness that would end the circumstance in which billionaires like Warren Buffett pay a lower percentage of their income in taxes than their secretaries.
Republicans cast it as a political gimmick and an attempt by President Barack Obama to give more Americans a "free ride."
It was blocked 51-45 in a filibuster vote. Republican Sen. Susan Collins of Maine and Democratic Sen. Mark Pryor of Arkansas were the only politicians to cross party lines.
"The wealthiest one percent takes home the highest share of the nation's income since the early '20s, the roaring '20s," Senate Majority Leader Harry Reid (D-Nev.) said. "Times are tough for many middle class American families. Millionaires and billionaires aren't sharing the pain or the sacrifice, not one bit. Last year there were 7,000 millionaires who didn't pay a single penny in federal income taxes."
Sen. Jon Kyl (R-Ariz.) countered that statistics show the rich are paying plenty, and that it's the bottom half of the income ladder that is doing too little.
"You've got the top 10 percent of taxpayers paying 70 percent of all the taxes, earning 45 percent of the income. Those are certainly the wealthy, and they're certainly paying a big share," Kyl argued. "How about less wealthy? The bottom 95 percent -- in other words, everybody but the top 5 percent -- pays 41.3 percent of income taxes, earns 65 percent of the money, of the income. Is this fair?
"The Joint Committee on Taxation estimates that 51 percent of all households, which includes both filers and nonfilers, had either zero or negative income tax liability in 2009," Kyl said, suggesting it was the middle class and poor who were not sacrificing. "People who do not share in the sacrifice of paying taxes have little direct incentive to care whether the government is spending and taxing too much. Maybe that's why the president has no problem with even more Americans getting a free ride."
The measure does not lower rates for the poor, but Democrats have said the $47 billion raised by the measure over 10 years would either go to deficit reduction or to help for middle class families.
"There are lots of ways that I think the American people would prefer to spend $47 billion than tax breaks for millionaires and billionaires who aren't paying what the average person pays," Sen. Chuck Schumer (D-N.Y.) said on a conference call with reporters before the vote.
Republicans countered that the evening vote was a "political gimmick" -- cooked up by Obama's campaign team -- that ignores the nation's critical problems, starting with its mounting debt.
“The problem is, we’ve got a president who seems more interested in pitting people against each other than he is in actually doing what it takes to face these challenges head on," Minority Leader Mitch McConnell (R-Ky.) said on the call, arguing that the Buffett Rule will never pass. "By wasting so much time on this political gimmick that even Democrats admit won’t solve our larger problems, it’s shown the president is more interested in misleading people than he is in leading."
"President Obama looked at the options in front of him, sat down with his political advisers, and he said, 'You know what, let’s go with the poll-tested tax increase on investment and job creation that won’t fix anything and won’t pass anyway,'" McConnell continued.
Indeed, the Democrats' position is popular. A CNN/ORC poll released Monday found that 72 percent of Americans favor taxing the very wealthy at 30 percent. The Buffet Rule would start phasing in at earnings above $1 million, and reach the full 30 percent for annual incomes above $2 million.
Democrats found McConnell's positions disingenuous, arguing before the vote that a GOP-waged filibuster would be the only reason for the Buffett Rule's failure.
"All of their arguments just don't stand up because they're so afraid of this issue," Schumer said on the call. "Are they for it or against it? They say, 'Well, it won't pass.' It won't pass because they are opposed to it," he said, adding that Republicans are the ones guilty of chicanery. "The gimmick is when they block something and say, 'Let's not pay attention to it because we won't let it pass.'"
Schumer vowed to keep bringing the Buffett Rule back until Republicans give in, the way they did on the payroll tax cut fight.
"We'll keep pushing this issue all year long, and we think we'll pick up more and more Republicans," Schumer said.
He added that the idea is not just to score campaign points, but to show people that Democrats are more in line with them on tax policy, and to ultimately pass the bill.
He suggested that the likely presence of Mitt Romney atop the GOP presidential ticket would help, because Romney has already been dubbed a poster child for the issue after paying a 13.9 percent tax rate on his last public return -- less than many in the middle class.
"It could be called the Buffett Rule, it could be called the Romney Rule," Schumer said. "I don't think he's going to want to have this present inequity remain when he's an example of it."
House Republicans are planning to counter the Buffett Rule push later this week with an attempt to cut taxes. A proposal by House Majority Leader Eric Cantor (R-Va.) would cut small business taxes by 20 percent. Since his bill would provide a disproportionately large benefit for the wealthy, it would mark an especially sharp contrast with the Democratic measure.
This story has been updated with a final vote tally.
Michael McAuliff covers politics and Congress for The Huffington Post. Talk to him on Facebook.