President Barack Obama supports changing the U.S. Constitution to keep private sector dollars from buying elections, campaign officials told Raw Story on background during a conference call with reporters Tuesday.

The decision stands in contrast with the president's recent embrace of super PAC campaigning, a key feature of the Supreme Court's controversial ruling in the Citizens United case. Super PACs are third-party groups not affiliated with political campaigns that are allowed to take and spend unlimited sums of money for or against candidates for public office.

"In recent months, we've seen super PACs affiliated with Republican presidential candidates spend more than $40 million on TV and radio, almost all of it on negative ads, not just against opponents but against the president," a top Obama campaign adviser said.

"Last week's filings showed that super PACs affiliated with Mitt Romney's campaign raised $30 million last year from fewer than 200 contributors, mostly from the financial sector. Governor Romney personally helped raise money from this group, which is run by some of his allies."

The campaign added: "Meanwhile, Karl Rove, the Koch brothers and others have joined together to raise almost a half billion dollars, again for one singular purpose: to defeat the president in November. So, with so much at stake, we're not going to allow a repeat of the 2010 election, where the Republican nominee is the beneficiary of Karl Rove-Koch brothers unlimited spending and the Democrats are unilaterally starving. There's too much at stake."

The decision means Obama is now welcoming the support of super PACs and endorsing the Priorities USA super PAC, which supports his reelection.

Meanwhile, the president has pledged to support a constitutional amendment that would reform campaign finance in such a way that outside groups are prohibited from spending unlimited sums on political advocacy.

That same path to reform was recently endorsed by Harvard professor Lawrence Lessig in his book "Republic, Lost," although he warned that Congress is not willing to commit such a change.

"We’ve been part of a process to get many people in many states to push their state legislatures to call for a convention, so that the convention can propose the changes that we as the American people need to consider," he said.