(CNN) – The fight over how best to tax the American people will turn to the personal finances of the two competing presidential candidates Friday, as President Barack Obama and Vice President Joe Biden plan to release their 2011 tax returns and issue a call for all-but-certain GOP nominee Mitt Romney to do the same.
The move comes after a week of aggressive promotion from the White House and Obama's reelection campaign on the so-called "Buffett Rule," a measure increasing the tax rate to 30% for Americans making more than $1 million per year.
Obama campaign spokesman Ben LaBolt confirmed the president and vice president's tax returns would be released Friday, and noted "the campaign will challenge Romney to do the same."
Romney's tax returns previously arose as an issue in January, when Democrats along with fellow Republican presidential candidates pressured Romney's campaign to release the documents.
On January 24, Romney's team released his 2010 tax return, as well as an estimate for 2011. Opponents quickly derided the disclosure as paltry, noting that other candidates, including Romney's father during his run for the GOP nomination in 1968, released a decade's worth of tax returns.
The forms the campaign did release showed Romney earned $42.7 million over the past two years and paid $6.2 million in taxes. Over the two years, Romney's effective tax rate - the percentage of his income that he owed in federal income taxes - was 14.5%.
Democrats, eager to align themselves with middle class voters, quickly assailed Romney for paying a low tax rate while earning millions of dollars.
On Thursday, Biden slammed Romney at a campaign stop in New Hampshire for promoting a "Romney Rule" on taxes that would benefit only millionaires like him – a harsh comparison to the "Buffett Rule" Democrats are promoting.
"The Buffett Rule says that multi-millionaires should pay at least the same percentage of their income in taxes as middle-class families do," Biden said Thursday. "The Romney Rule says the very wealthy should keep the tax cuts and loopholes they have, and get an additional, new tax cut every year that is worth more than what the average middle class family makes in an entire year."
Anticipating the pressure to release Romney's tax returns, the former Massachusetts governor's campaign said Obama's campaign was diverting attention from a failed economic record.
"It's no surprise with the worst job creation record in modern history that President Obama would try to distract Americans from the real issues with a series of sideshows," Romney campaign spokeswoman Andrea Saul said. "Gov. Romney has already released his 2010 return and an estimate of his 2011 income and taxes. He will release his full 2011 return when it is filed."
Obama's 2010 tax return showed the president earned $1,728,096 and paid $453,770 in income taxes.
CNN's Jim Acosta and Paul Steinhauser and CNNMoney's Jeanne Sahadi contributed to this report.