The vote came the day before Americans' annual taxes are due.
The 51-45 count along party lines was designed more to win over voters and embarrass senators in close races this election year than to push legislation into law.
Obama denounced the vote, saying: "It's just plain wrong that millions of middle-class Americans pay a higher share of their income in taxes than some millionaires and billionaires."
Republicans called the measure a divisive Democratic distraction from the nation's real problems.
"This legislation will do nothing with regard to job creation, with regard to gas prices, with regard to economic recovery," said Senator Jon Kyl, the No. 2 Senate Republican leader.
Monday's vote was the first time a so-called "Buffett rule" proposal has come to a Senate vote this election year. Citing complaints from billionaire Warren Buffett that he pays a lower tax rate than his secretary, Obama has said everyone earning at least $1 million a year or more should pay at least 30% of their income in taxes.
With presidential and congressional elections approaching in November, the vote was a glimpse of the broader battle the two parties are waging over an economy that's still having a tough time creating enough new jobs.
Read more at the Guardian...