FEC rules regulating the earmarking of money and proliferation of PACs for this very purpose would prevent it from happening, she argued.

In response to questions from Justices Elena Kagan and Kennedy about the possibility that 100 different PACs might be set up to funnel donations to five specific candidates — allowing donors to legally give each PAC $5,000, which then passed on $1,000 to each candidate, keeping the donor within the per PAC limits but effectively allowing a donation of $500,000 to a candidate — Shaun McCutcheon’s attorney, Erin Murphy, said it just wasn’t plausible.

One was that there’s an active and functioning FEC that will nip at any trespassers.

Today’s argument in McCutcheon over whether aggregate limits on a single donor’s contributions to candidates, parties and PACs should be scrapped revealed other assumptions that may have a tenuous connection to reality.

In that case, Justice Anthony Kennedy wrote for the majority that donor disclosure would keep everything on the up-and-up. As it turns out, though, the role of “dark money” groups — whose contributors need not be revealed, according to the FEC — has exploded since the Supreme Court issued that opinion.

Could a decision inbe based on misconceptions about how campaign finance actually works — much as the 2010decision was?

“I don’t think it’s a particularly realistic scenario under existing regulations,” Murphy told the justices. “I think that if you look at it, if you have a bunch of PACs that are getting contributions from this same group of individuals, you are going to run into earmarking and proliferation restrictions.”

Bob Biersack, a 30-year veteran of the Federal Election Commission and the Center for Responsive Politics’ senior fellow, said that current restrictions might keep a single person from coordinating the hypothetical 100 different PACs — but they wouldn’t prohibit 100 different like-minded individuals from organizing 100 different PACs to support five specific candidates.

“While there are some restrictions on directing contributions to third parties and simply creating multiple PACs, those restrictions don’t prevent the creation of multiple committees (by different people) with common goals,” Biersack said. “These could be used to bring more money from a single donor to bear on a few important races.”

Current aggregate limits cap any one donor to giving a maximum of $123,200 in each two- year cycle ($48,600 to all candidates and $74,600 to all PACs and parties). Without that overall cap, supporters of the aggregate limits cite a scenario where one donor could give as much as $3.6 million in one cycle — the maximum to a candidate in 435 House races and 33 Senate races, and the maximum to 50 state parties and all national party groups. Supporters of the limit claim the money could then be shifted between the groups and sent to a designated recipient, making it possible to circumvent the limits on how much a donor can give to any one particular candidate or committee.

Justice Alito, in particular, seemed skeptical that money could easily be transferred between parties, committees and candidates, saying it just wasn’t realistic that one donor might make donations of $3.6 million to all of the available committees and candidates and those groups would turn around and funnel it all to one needy candidate.

“What troubles me about your argument, [Solicitor General Donald] Verilli … is that what I see are wild hypotheticals that are not obviously plausible and lack certainly any empirical support,” Alito told the solicitor general.

Limits on donations to candidates, committees and parties would mean that an individual would have to make those gifts to many different groups and hope they funnel them to the donor’s intended target — even if there was no limit on how much a donor could give overall. It’s hard to believe, Alito said, that the money could get from Point A to Point B.

“You have to get it from the person who wants to corrupt to the person who is going to be corrupted. Unless the money can make it from Point A to Point B, I don’t see where the quid pro quo argument is,” Alito said.

Alito seemed to doubt that the many different committees, party organizations and candidates could actually coordinate to funnel a donor’s large $3.6 million donation to one needy recipient.

But CRP data shows that even under the current system, there is intense shuffling of money — between outside groups like super PACs and politically active nonprofits (a phenomena we call “churning” ) and also between parties, candidates, committees and joint-fundraising efforts

And state parties and hundreds of candidates already transfer large sums of money to each other, using the national party groups as hubs.

And in 2012, Democratic state and local parties transferred $4.6 million to national party organizations, and their Republican counterparts transferred $31.7 million.

Scalia also challenged the idea that $3.5 million (Scalia and several other justices used both $3.6 million and $3.5 million in their questioning) in donations from one individual would actually be much of a big deal. When Verilli estimated that in 2010, each side raised about $1.5 billion for the congressional elections, Scalia scoffed that taking the aggregate cap off an individual donor would make a difference.

“When you add all that up, I don’t think $3.5 million is all that much,” Scalia said.

According to CRP data, though, $3.5 million is actually fairly significant. Even in 2012, the most expensive election ever, the average winner of a House race spent only $1.5 million . In other words, at the current spending levels, each donor who gave $3.5 million could fund, on average, two winning House campaigns — and have change left over.

In direct response to Scalia, Verilli pointed out that each side would only need 450 mega-donors giving the $3.5 million to reach the $1.5 billion raised in 2010.

“Less than 500 people can fund the whole shooting match,” Verilli replied. “You are going to create a situation, if you take off of the aggregate limits, in which there is a very real risk that the government will be run of, by, and for those 500 people and that the public will perceive that the government is being run of, by, and for those 500 people.”

The number of Americans giving a significant amount of money to federal political candidates is already a fairly exclusive club, according to CRP data. Of an estimated 310 million Americans, only about 241,000 of us gave more than $2,500 in the 2012 election cycle — about 0.08 percent of the population. Yet those 0.08 percent of Americans accounted for $2.1 billion in contributions in 2012.

Arguments that there could be an elite class of donors funding “the whole shooting match”, didn’t seem to sway several of the conservative justices. While Verilli focused on how much more exclusive the club of donors could become, several conservative members of the court seemed focused on the concern that if aggregate limits keep even one donor from giving all they might want to give, that donor’s First Amendment rights are infringed.

“I appreciate the argument you are making about the 3-point-whatever million-dollar check and the need for the aggregate limits to address that,” Chief Justice John Roberts told Verilli. “But what do you do with the flip side? I mean, you can’t pretend that this is pursued with no First Amendment cost.”

Under current aggregate limits, an individual donor can give the maximum donation to only nine federal candidates. The danger of a donor giving $3.5 million may be real, Roberts said, but restricting that donor violates his or her right to give $5,200 to 10 or 11 candidates, instead of the currently acceptable nine.