It turns out that President Obama also pays a lower tax rate than his secretary, just like billionaire investor Warren Buffett.

That's one of the reasons Obama backs the so-called Buffett Rule, the subject of a Senate debate today, aides said.

"That is the point of the Buffett Rule," said White House spokesman Jay Carney. "The tax code should not be written in a way that allows the wealthiest Americans to pay taxes at a lower rate than middle-class Americans."

The Senate is scheduled to vote later today on the Buffett Rule, which would require millionaires and billionaires to pay at least the same tax rate as middle-class Americans.

It is likely to be blocked by Republicans who call the plan nothing more than an election year gimmick.

The proposal is named for Buffett because he too has protested paying a lower tax rate than his secretary.

Obama himself would not qualify for the Buffett Rule, which would apply only to people who make more than $1 million in a particular year.

The president and first lady Michelle Obama reported adjusted gross income of $789,674 for 2011. They paid out $162,074 in federal tax -- a rate of 20.5%.

One reason for the relatively low rate: The Obamas donated about 22% of their income to charity.

The Democratic-run Senate may be able to forge a majority for the Buffett Rule, but the GOP has the numbers to filibuster.

Senate Minority Leader Mitch McConnell, R-Ky., and other Republicans say Obama and the Democrats should focus on jobs rather than on arbitrary take hikes on job creators.

Likely Republican presidential nominee Mitt Romney -- and a target of the Buffett Rule push -- says Obama is trying to divide Americans.

"The new source of division is to say, 'let's find the very most successful in our country and say they're bad guys,'" Romney said at a recent campaign stop. "'Go after 'em. And let's divide America.'"