Senate Democrats readied a vote on the so-called Buffett Rule that would raise taxes on millionaires as Republicans fired back that the tax would depress investment and the economy.

With President Barack Obama leading the charge, Democrats have been framing the issue as a matter of fairness, complaining that people who make more than $1 million a year have unfair tax advantages. The proposed rule would require Americans earning more than $1 million a year to pay a 30% overall federal tax rate

Republicans cry class warfare, and point to government statistics showing that people making more than $1 million account for a tiny fraction of the population, but pay almost a quarter of U.S. individual income taxes.

“This entire debate has been very illuminating,” Senate Minority Leader Mitch McConnell (R., Ky.) said on the Senate floor. “By wasting so much time on this political gimmick, that shows the president is actually more interested in misleading people than he is in leading.”