Barack Obama has a radical idea for how to reform campaign finance: amend the Constitution.

The president told Vox in an exclusive interview that he wants to see such a drastic change, because he thinks the money-in-politics status quo is so damaging to our political system.

Arguing that "unlimited money" in politics is a key cause of polarization, Obama said, "I would love to see some constitutional process that would allow us to actually regulate campaign spending the way we used to, and maybe even improve it."

These comments — made in the midst of a long, big-picture response to a question on political polarization, during which several issues were discussed — go further than many of the president's past public statements. During a Q&A with Reddit in 2012, the president wrote that "over the long term, I think we need to seriously consider mobilizing a constitutional process to overturn Citizens United." But he's given little attention to the topic during his second term so far.

Clearly, though, the president's still not happy with the status quo, and would prefer a change. He's floating an aggressive idea that may sound implausible, considering the hurdles involved in a constitutional amendment. It's an idea, though, that most other top Democrats have already embraced.

So here's a look at where Obama is on the issue of campaign finance — and what such a constitutional amendment might actually look like.

Obama's past positions on election spending

The president's history on the campaign finance issue is somewhat fraught. As he was raising record sums during his 2008 presidential campaign, he became the first major-party presidential nominee to decline public funds since the public funding system was created. He did so because he didn't want to abide by the spending limits that came with those funds — and because he knew he could easily out-raise his rival, Sen. John McCain. But he faced heavy criticism for flip-flopping on a seeming campaign commitment, and for weakening the norm that all presidential nominees accept public funds.

Once Obama's presidency began, the issue of campaign finance reform got relatively little attention until the Supreme Court's Citizens United ruling came down in January 2010. Days later, in his State of the Union address, Obama condemned the ruling as several Supreme Court justices sat in front of him, and said it would allow "special interests — including foreign corporations — to spend without limit in our elections."

His focus on foreign corporations was criticized as misleading: in the audience, justice Sam Alito famously mouthed the words "not true," since the majority opinion didn't address the issue of foreign spending. But his concern about unlimited spending proved to be well-founded. Outside groups' spending on federal elections exploded in the years after the ruling, soaring from $338 million in 2008 to over $1 billion in 2012, according to the Center for Responsive Politics.

The Supreme Court ruling couldn't be reversed by a new law, so Democrats decided instead to focus on increasing disclosure requirements. Obama urged the Senate to pass a bill to that effect in 2010, but it was blocked by a Republican filibuster. And once the GOP took the House that fall, further campaign finance legislation was clearly dead.

Publicly, Obama only infrequently mentioned campaign finance reform after that. But privately, he was promising something very different. At a February 2012 fundraiser in Seattle, Obama told a group of donors — including Bill Gates — that his reelection "may allow me to use the bully pulpit to argue forcefully for a constitutional amendment" on campaign finance, according to Ken Vogel's book Big Money.

Vogel quotes Obama saying "I taught constitutional law" and "I don't tinker with the Constitution lightly. But I think this is important enough that citizens have to get mobilized around this issue." Obama added, "After my reelection, my sense is that I may be in a very strong position to do it."

What such an amendment might look like

The proposal for a constitutional amendment the Senate considered last fall— which received the support of every Senate Democrat, but failed to gain the two-thirds support necessary for approval — is one example of what campaign finance reformers are looking to achieve. It doesn't merely reverse the Citizens United v. FEC ruling, but goes back decades further.

Reformers think the Supreme Court has defined corruption too narrowly

Since 1976, when the Supreme Court has considered whether certain restrictions on election spending are constitutional, it has taken two main things into account. On the one hand there's the First Amendment right to freedom of speech — which the Court believes includes the spending of money on elections — and on the other hand there's a governmental interest in preventing corruption or the appearance of corruption.

The problem, as campaign finance reformers see it, is that for decades, the Supreme Court has defined speech too broadly, and corruption too narrowly. It has ruled that laws capping how much an individual or group can donate to a particular candidate are acceptable, because they help prevent corruption. However, overall caps on the amount any candidate or corporation spends on elections are unconstitutional, because they muzzle speech without specifically preventing corruption. (The court's narrow definition of "corruption" has consistently been disputed by some justices in the minority.)

So the Democrats' proposed constitutional amendment specifically says that both Congress and state governments can limit the "raising and spending of money" meant "to influence elections." It lists several rationales for doing so — advancing "democratic self-government," "political equality," and protecting the "integrity" of the political process. However, it only says that "reasonable limits" are acceptable — so if the amendment is ever enacted, there would undoubtedly be court battles over which restrictions are reasonable or unreasonable.

Republicans have argued that this amendment would alter the Bill of Rights for the first time in history. However, the amendment itself wouldn't actually have altered any text in the First Amendment, or the Bill of Rights more generally. Instead, it would have shot down the current Supreme Court majority's interpretation that the First Amendment prevents caps on election spending. Much of this interpretation was laid out in the 1976 case Buckley v. Valeo, and it was expanded on by several more recent Roberts Court rulings. But the interpretation has always been controversial, even within the Court itself — the recent major campaign finance rulings have all been 5 to 4.

The challenges ahead for campaign finance reform

To pass even a law reforming campaign finance, like the 2002 McCain-Feingold law, some bipartisanship is necessary. A constitutional amendment is a much bigger lift — requiring two-thirds approval in the House and Senate, and further approval from 38 states.

And the biggest problem that has dogged campaign finance reform activists is just that topic Obama discussed in his interview with Vox: polarization. The issue has become completely polarized by party, with Republicans overwhelmingly opposed to more restrictions. Indeed, when the proposed constitutional amendment went before the Senate, every Democrat present voted yes and every Republican present voted no.

That's why activist Lawrence Lessig, hoping to boost a solitary GOP reformer to the Senate, backed a primary challenger to Scott Brown in New Hampshire's Senate race this year. But the issue clearly didn't resonate enough with the state's primary voters, and Brown won by a wide margin. "We lost. Badly," Lessig wrote afterward. "There's no spinning this." Brown went on to lose the general election, but the point was made — it's been really tough for campaign finance reformers to get even one Republican on their side.

So while Obama may believe that big money in politics causes polarization, he's also aware that the potential reforms addressing the issue are themselves polarizing. To Vox, he characterized the reform as one of several "structural things that I'd like to see that I think would improve this."

But, knowing it's unlikely to happen anytime soon, he went on to argue that things might not be so bad, historically. "You know there’ve been periods in the past where we've been pretty polarized. I think, there just wasn't polling around. As I recall there was a whole civil war," Obama said. "That was a good example of polarization that took place."