TAMPA, Fla. -- President Barack Obama suggested he would support beginning an effort to amend the U.S. Constitution to undo a Supreme Court decision that gave way to the rise of so-called "Super PACs."

In a chat on the social media website Reddit, the president told readers that he would back an amendment to counteract the impact of the court's ruling in Citizens United v. FEC, a 2010 decision that did away with limits on corporate and labor spending in elections.

"Over the longer term, I think we need to seriously consider mobilizing a constitutional amendment process to overturn Citizens United (assuming the Supreme Court doesn't revisit it)," the president wrote. "Even if the amendment process falls short, it can shine a spotlight of the super PAC phenomenon and help apply pressure for change."

The president said he still supports the Disclose Act, which would force greater transparency from outside spending groups in disclosing their sources of funding. Obama also emphasized his support for banning lobbyists from the practice of "bundling," or raising large sums of contribution from a group of donors.

The 2012 campaign has seen an unprecedented influx of political spending due to the rise of super PACs, which are able to raise and spend unlimited sums on electioneering. Many of those groups also have twin nonprofit arms, which are able to raise and spend millions on "issue advocacy" without having to disclose its funding source.

Both Obama and his Republican opponent, Mitt Romney, have super PACs spending on their behalf this cycle. Obama reluctantly endorsed his, Priorities USA Action, after having initially opposed the groups;

Arizona Sen. John McCain predicted a renewed effort of reform the nation's campaign finance laws as an outgrowth of the unrestrained influx of donations in this year's presidential campaign. 

The Supreme Court's 2010 decision in the Citizens United case, which struck down many of the restrictions on political spending and spurred the advent of so-called "super PACs," was one of the worst in modern history, McCain said. 

"I think there will be scandals as associated with the worst decision of the Supreme Court in the 21st Century — uninformed, arrogant, naive," McCain said on NBC's "Meet the Press."

"The fact is that the system is broken," he later added. "I predict to you that there will be scandals, and I predict to you that there will be reform again."

McCain has long been an advocate of campaign finance reform; a landmark 2002 campaign finance law bearing his name was the subject of the legal challenge that led to the Citizens United ruling. 

That decision did away with many of the limits on the magnitude of political contributions, fueling an inflation in the cost of campaigns, particularly on the federal level. Super PACs like American Crossroads, Restore our Future and Priorities USA Action have been able to spend tens of millions of dollars already on the campaign. They're able to cull their support from a handful of wealthy donors, the size of whose report is sometimes clouded by twin nonprofit groups associated with super PACs, which don't have to disclose their donors. 

One of the largest such donors has been Sheldon Adelson, the casino magnate who gave over $10 million to a super PAC in the primary that supported Newt Gingrich for president. Adelson's since pledged at least $10 million to the pro-Romney super PAC, Restore Our Future. 

McCain fretted earlier this week that Adelson's contributions would be tantamount to "foreign money" entering the campaign, since Adelson's fortune is built in part by revenues from overseas casinos. 

McCain said on Sunday that he's worried about Adelson's influence, but no more so than the influence of organized labor spending or other donors' impact on the campaign.

"Not any more than other people who will give lots of money; not any more than the trade unions, the labor unions have. The whole system's broken, and there's a wash. I don't pick out Mr. Adelson any more than I pick out Mr. Trumka," he said, referring to the AFL-CIO's president.

The political undertones of President Obama's energy-related tour of swing states haven't been lost by the Republican super PAC American Crossroads, which launched new TV ads in the states where the president will stop.

As NBC News’ Ali Weinberg pointed out, Obama's tour will tout his energy policies in states that have stubbornly high gas prices.

But Crossroads, the brainchild of former Bush operatives Karl Rove and Ed Gillespie, isn't content to let that message go uncontested; the group made a $650,000 ad buy in Albuquerque, Las Vegas and Columbus -- the major media markets near the locations of Obama's stops.

The blistering attack ad suggests that the Obama administration allowed for gas to go up by $2 dollars a gallon, and neglected to develop American oil shale or support construction of the Keystone pipeline. It also uses sound from National Journal’s Major Garrett, who says in the ad: “At the White House for 3 weeks, the word has been deflect or shield on gas prices. Put up the deflector shield.”

The ad can be seen here:

The size and scope of the ad buy demonstrates the influences of these deep-pocketed super PACs during the 2012 election cycle. Instead of dominating the local airwaves with his own message in swing states, the president will have to contend with countermessaging from a well-funded group of mainly unknown donors pushing back on his every word.

President Obama's re-election campaign made an about-face late Monday in its opposition to super PACs, encouraging donors to send their unlimited contributions to one such group founded by a former administration spokesman. 

Obama campaign manager Jim Messina emailed supporters to formally endorse contributions to Priorities USA, the Democratic super PAC founded by Bill Burton, a former White House deputy press secretary. 

"With so much at stake, we can't allow for two sets of rules in this election whereby the Republican nominee is the beneficiary of unlimited spending and Democrats unilaterally disarm," Messina wrote on the campaign's blog. "Therefore, the campaign has decided to do what we can, consistent with the law, to support Priorities USA in its effort to counter the weight of the GOP Super PAC."

The decision represents a stark reversal for Obama, who has been among the most vocal critics of these outside political spending groups since the Supreme Court's 2010 ruling that paved the way for the rise of super PACs. 

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Obama has led Democrats in opposition to these groups, especially at the height of 2010's congressional elections. Republican-aligned groups like American Crossroads and Crossroads GPS took advantage of the new rules to great effect, spending tens of millions of dollars against Democrats during that election. 

"And thanks to a Supreme Court decision called Citizens United, they are being helped along this year by special interest groups that are spending unlimited amounts of money on attack ads … without ever disclosing who’s behind all these attack ads," Obama said of Republicans and super PACs that fall. "Now, that’s not just a threat to Democrats — that’s a threat to our democracy."

The president expressed his alarm as recently as Sunday in an interview with TODAY's Matt Lauer: "One of the worries we have obviously in the next campaign is that there are so many of these so-called super PACs, these independent expenditures that are gonna be out there," he said in a pre-Super Bowl interview.

'Smell test'
Moreover, after Priorities USA had launched, the White House continued to encourage it to abide by a stricter set of rules and disclose its donors. As recently as last week, Senate Democrats had announced their intention to investigate these groups, with New York Sen. Chuck Schumer (D) arguing that the notion that groups like these don't coordinate a failure of the "smell test."

The Obama campaign's reversal, though, is a testament to the effectiveness of these groups. Restore Our Future, a super PAC established on behalf of Mitt Romney, has raised tens of millions of dollars already and spent some of that war chest with great effectiveness against Romney's rivals in the Republican primary. 

Messina's statement Monday evening said that senior campaign officials, along with some White House and cabinet officials, would attend events and solicit donations for Priorities USA. Those actions are permitted under federal election laws, though Priorities USA is barred from coordinating formally with the Obama campaign. (Messina said that Obama, Vice President Biden and the first lady would not participate in this effort.)

"As has become evident in the past month, the only enthusiasm in the Republican Party is among oil company billionaires and investment bankers on Wall Street looking to defeat President Obama," Burton said by email in reaction to the decision. "We’re committed to providing a balance to Karl Rove and the Koch brothers who have pledged more than half a billion dollars to their effort."

According to a filing this month with the Federal Election Commission, Priorities USA Action had managed to raise about $1.2 million in the second half of 2011, leaving it with about $1.5 million in the bank at the end of the year. 

With the heft of the Obama campaign behind its efforts, though, Priorities USA could see its bank accounts swell, giving the group millions to spend on behalf of the president — and agains his eventual Republican challenger — over the course of the next nine months.